diff --git a/harness/temporalHelpers.js b/harness/temporalHelpers.js
index 4fe2ca1258..78f20a0d59 100644
--- a/harness/temporalHelpers.js
+++ b/harness/temporalHelpers.js
@@ -342,7 +342,7 @@ var TemporalHelpers = {
     const actual = [];
     const expected = [];
 
-    const calendar = new Temporal.Calendar("iso8601");
+    const calendar = "iso8601";
     const datetime = new Temporal.PlainDateTime(2000, 5, 2, 12, 34, 56, 987, 654, 321, calendar);
     const prototypeDescrs = Object.getOwnPropertyDescriptors(Temporal.PlainDateTime.prototype);
     ["year", "month", "monthCode", "day", "hour", "minute", "second", "millisecond", "microsecond", "nanosecond"].forEach((property) => {
@@ -964,8 +964,7 @@ var TemporalHelpers = {
     const actual = [];
     const expected = [];
 
-    const calendar = new Temporal.Calendar("iso8601");
-    const date = new Temporal.PlainDate(2000, 5, 2, calendar);
+    const date = new Temporal.PlainDate(2000, 5, 2, "iso8601");
     const prototypeDescrs = Object.getOwnPropertyDescriptors(Temporal.PlainDate.prototype);
     ["year", "month", "monthCode", "day"].forEach((property) => {
       Object.defineProperty(date, property, {
diff --git a/test/built-ins/Temporal/Duration/compare/relativeto-propertybag-invalid-offset-string.js b/test/built-ins/Temporal/Duration/compare/relativeto-propertybag-invalid-offset-string.js
index c1dfe588e1..42deeb54db 100644
--- a/test/built-ins/Temporal/Duration/compare/relativeto-propertybag-invalid-offset-string.js
+++ b/test/built-ins/Temporal/Duration/compare/relativeto-propertybag-invalid-offset-string.js
@@ -7,7 +7,6 @@ description: relativeTo property bag with offset property is rejected if offset
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
 const d1 = new Temporal.Duration(0, 1, 0, 280);
 const d2 = new Temporal.Duration(0, 1, 0, 281);
 
@@ -21,7 +20,7 @@ const badOffsets = [
   1000n,      // must be a string
 ];
 badOffsets.forEach((offset) => {
-  const relativeTo = { year: 2021, month: 10, day: 28, offset, timeZone };
+  const relativeTo = { year: 2021, month: 10, day: 28, offset, timeZone: "UTC" };
   assert.throws(
     typeof(offset) === 'string' ? RangeError : TypeError,
     () => Temporal.Duration.compare(d1, d2, { relativeTo }),
diff --git a/test/built-ins/Temporal/Duration/prototype/round/relativeto-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/Duration/prototype/round/relativeto-propertybag-calendar-wrong-type.js
index ee0b727846..8fd96253b3 100644
--- a/test/built-ins/Temporal/Duration/prototype/round/relativeto-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/Duration/prototype/round/relativeto-propertybag-calendar-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.Duration(1, 0, 0, 0, 24);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/Duration/prototype/round/relativeto-propertybag-invalid-offset-string.js b/test/built-ins/Temporal/Duration/prototype/round/relativeto-propertybag-invalid-offset-string.js
index 92729decd6..ee038cd8b4 100644
--- a/test/built-ins/Temporal/Duration/prototype/round/relativeto-propertybag-invalid-offset-string.js
+++ b/test/built-ins/Temporal/Duration/prototype/round/relativeto-propertybag-invalid-offset-string.js
@@ -7,7 +7,7 @@ description: relativeTo property bag with offset property is rejected if offset
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.Duration(1, 0, 0, 0, 24);
 
 const badOffsets = [
diff --git a/test/built-ins/Temporal/Duration/prototype/round/relativeto-wrong-type.js b/test/built-ins/Temporal/Duration/prototype/round/relativeto-wrong-type.js
index d4b7af3f67..22fc458dec 100644
--- a/test/built-ins/Temporal/Duration/prototype/round/relativeto-wrong-type.js
+++ b/test/built-ins/Temporal/Duration/prototype/round/relativeto-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone('UTC');
+const timeZone = "UTC";
 const instance = new Temporal.Duration(1, 0, 0, 0, 24);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/Duration/prototype/total/relativeto-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/Duration/prototype/total/relativeto-propertybag-calendar-wrong-type.js
index aba5db54ef..89d8002d2a 100644
--- a/test/built-ins/Temporal/Duration/prototype/total/relativeto-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/Duration/prototype/total/relativeto-propertybag-calendar-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.Duration(1, 0, 0, 0, 24);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/Duration/prototype/total/relativeto-propertybag-invalid-offset-string.js b/test/built-ins/Temporal/Duration/prototype/total/relativeto-propertybag-invalid-offset-string.js
index 50b44cb62a..f5adc67f93 100644
--- a/test/built-ins/Temporal/Duration/prototype/total/relativeto-propertybag-invalid-offset-string.js
+++ b/test/built-ins/Temporal/Duration/prototype/total/relativeto-propertybag-invalid-offset-string.js
@@ -7,7 +7,7 @@ description: relativeTo property bag with offset property is rejected if offset
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.Duration(1, 0, 0, 0, 24);
 
 const badOffsets = [
diff --git a/test/built-ins/Temporal/Duration/prototype/total/relativeto-wrong-type.js b/test/built-ins/Temporal/Duration/prototype/total/relativeto-wrong-type.js
index d90ba1dc14..29541d661e 100644
--- a/test/built-ins/Temporal/Duration/prototype/total/relativeto-wrong-type.js
+++ b/test/built-ins/Temporal/Duration/prototype/total/relativeto-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone('UTC');
+const timeZone = "UTC";
 const instance = new Temporal.Duration(1, 0, 0, 0, 24);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/Instant/prototype/toString/timezone-offset.js b/test/built-ins/Temporal/Instant/prototype/toString/timezone-offset.js
index 1914167cf0..f2e4f93327 100644
--- a/test/built-ins/Temporal/Instant/prototype/toString/timezone-offset.js
+++ b/test/built-ins/Temporal/Instant/prototype/toString/timezone-offset.js
@@ -10,8 +10,7 @@ features: [BigInt, Temporal]
 const instant = new Temporal.Instant(0n);
 
 function test(timeZoneIdentifier, expected, description) {
-  const timeZone = new Temporal.TimeZone(timeZoneIdentifier);
-  assert.sameValue(instant.toString({ timeZone }), expected, description);
+  assert.sameValue(instant.toString({ timeZone: timeZoneIdentifier }), expected, description);
 }
 
 test("UTC", "1970-01-01T00:00:00+00:00", "offset of UTC is +00:00");
diff --git a/test/built-ins/Temporal/Instant/prototype/toZonedDateTimeISO/branding.js b/test/built-ins/Temporal/Instant/prototype/toZonedDateTimeISO/branding.js
index a5997e2f01..021dbb0d81 100644
--- a/test/built-ins/Temporal/Instant/prototype/toZonedDateTimeISO/branding.js
+++ b/test/built-ins/Temporal/Instant/prototype/toZonedDateTimeISO/branding.js
@@ -11,7 +11,7 @@ const toZonedDateTimeISO = Temporal.Instant.prototype.toZonedDateTimeISO;
 
 assert.sameValue(typeof toZonedDateTimeISO, "function");
 
-const args = [{ timeZone: new Temporal.TimeZone("UTC") }];
+const args = [{ timeZone: "UTC" }];
 
 assert.throws(TypeError, () => toZonedDateTimeISO.apply(undefined, args), "undefined");
 assert.throws(TypeError, () => toZonedDateTimeISO.apply(null, args), "null");
diff --git a/test/built-ins/Temporal/PlainDate/from/argument-propertybag-calendar.js b/test/built-ins/Temporal/PlainDate/from/argument-propertybag-calendar.js
index c1b6eb5de3..618bbfb15d 100644
--- a/test/built-ins/Temporal/PlainDate/from/argument-propertybag-calendar.js
+++ b/test/built-ins/Temporal/PlainDate/from/argument-propertybag-calendar.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const calendar = new Temporal.Calendar("iso8601");
+const calendar = "iso8601";
 const plainDate = Temporal.PlainDate.from({ year: 1976, month: 11, day: 18, calendar });
 TemporalHelpers.assertPlainDate(plainDate, 1976, 11, "M11", 18);
 assert.sameValue(plainDate.getISOFields().calendar, "iso8601", "calendar slot should store a string");
diff --git a/test/built-ins/Temporal/PlainDate/from/argument-zoneddatetime.js b/test/built-ins/Temporal/PlainDate/from/argument-zoneddatetime.js
index eee8e4b0c1..3caa472f66 100644
--- a/test/built-ins/Temporal/PlainDate/from/argument-zoneddatetime.js
+++ b/test/built-ins/Temporal/PlainDate/from/argument-zoneddatetime.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const calendar = new Temporal.Calendar("iso8601");
+const calendar = "iso8601";
 const zdt = new Temporal.ZonedDateTime(1_000_000_000_987_654_321n, "UTC", calendar);
 const result = Temporal.PlainDate.from(zdt);
 
diff --git a/test/built-ins/Temporal/PlainDate/prototype/equals/argument-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/PlainDate/prototype/equals/argument-propertybag-calendar-wrong-type.js
index 1cab7c1e23..a91bbe8e2d 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/equals/argument-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/equals/argument-propertybag-calendar-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.PlainDate(2000, 5, 2);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/PlainDate/prototype/since/argument-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/PlainDate/prototype/since/argument-propertybag-calendar-wrong-type.js
index cabc64bba1..d6fa356f70 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/since/argument-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/since/argument-propertybag-calendar-wrong-type.js
@@ -9,7 +9,6 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
 const instance = new Temporal.PlainDate(2000, 5, 2);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/PlainDate/prototype/toPlainMonthDay/basic.js b/test/built-ins/Temporal/PlainDate/prototype/toPlainMonthDay/basic.js
index c64b637bc3..219942a325 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/toPlainMonthDay/basic.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/toPlainMonthDay/basic.js
@@ -8,8 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const calendar = new Temporal.Calendar("iso8601");
-const pd = new Temporal.PlainDate(1970, 12, 24, calendar);
+const pd = new Temporal.PlainDate(1970, 12, 24, "iso8601");
 const pmd = pd.toPlainMonthDay();
 TemporalHelpers.assertPlainMonthDay(pmd, "M12", 24);
 assert.sameValue(pmd.getISOFields().calendar, "iso8601");
diff --git a/test/built-ins/Temporal/PlainDate/prototype/toPlainYearMonth/basic.js b/test/built-ins/Temporal/PlainDate/prototype/toPlainYearMonth/basic.js
index d2c722c514..01c41f225f 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/toPlainYearMonth/basic.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/toPlainYearMonth/basic.js
@@ -8,8 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const calendar = new Temporal.Calendar("iso8601");
-const pd = new Temporal.PlainDate(1970, 12, 24, calendar);
+const pd = new Temporal.PlainDate(1970, 12, 24, "iso8601");
 const pym = pd.toPlainYearMonth();
 TemporalHelpers.assertPlainYearMonth(pym, 1970, 12, "M12");
 assert.sameValue(pym.getISOFields().calendar, "iso8601");
diff --git a/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/basic.js b/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/basic.js
index 99591700ca..47c909eef3 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/basic.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/basic.js
@@ -8,7 +8,7 @@ features: [Temporal]
 ---*/
 
 const plainDate = Temporal.PlainDate.from("2020-01-01");
-const timeZone = Temporal.TimeZone.from("UTC");
+const timeZone = "UTC";
 const plainTime = Temporal.PlainTime.from("12:00");
 
 let result = plainDate.toZonedDateTime({ timeZone, plainTime });
@@ -17,13 +17,7 @@ assert.sameValue(result.toString(), "2020-01-01T12:00:00+00:00[UTC]", "objects p
 result = plainDate.toZonedDateTime(timeZone);
 assert.sameValue(result.toString(), "2020-01-01T00:00:00+00:00[UTC]", "time zone object argument");
 
-result = plainDate.toZonedDateTime("UTC");
-assert.sameValue(result.toString(), "2020-01-01T00:00:00+00:00[UTC]", "time zone string argument");
-
-result = plainDate.toZonedDateTime({ timeZone });
-assert.sameValue(result.toString(), "2020-01-01T00:00:00+00:00[UTC]", "time zone object property");
-
-result = plainDate.toZonedDateTime({ timeZone: "UTC", plainTime });
+result = plainDate.toZonedDateTime({ timeZone, plainTime });
 assert.sameValue(result.toString(), "2020-01-01T12:00:00+00:00[UTC]", "time zone string property");
 
 result = plainDate.toZonedDateTime({ timeZone, plainTime: "12:00" });
diff --git a/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/branding.js b/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/branding.js
index 6ef14dad48..e035cdfbec 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/branding.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/branding.js
@@ -11,7 +11,7 @@ const toZonedDateTime = Temporal.PlainDate.prototype.toZonedDateTime;
 
 assert.sameValue(typeof toZonedDateTime, "function");
 
-const args = [new Temporal.TimeZone("UTC")];
+const args = ["UTC"];
 
 assert.throws(TypeError, () => toZonedDateTime.apply(undefined, args), "undefined");
 assert.throws(TypeError, () => toZonedDateTime.apply(null, args), "null");
diff --git a/test/built-ins/Temporal/PlainDate/prototype/until/argument-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/PlainDate/prototype/until/argument-propertybag-calendar-wrong-type.js
index e0383ce83e..8c8d042319 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/until/argument-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/until/argument-propertybag-calendar-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.PlainDate(2000, 5, 2);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/PlainDate/prototype/withCalendar/basic.js b/test/built-ins/Temporal/PlainDate/prototype/withCalendar/basic.js
index c6845db76e..cabe8538d2 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/withCalendar/basic.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/withCalendar/basic.js
@@ -9,20 +9,9 @@ features: [Temporal]
 ---*/
 
 const plainDate = Temporal.PlainDate.from("1976-11-18");
-const calendar = Temporal.Calendar.from("iso8601");
-
-const objectResult = plainDate.withCalendar(calendar);
-assert.notSameValue(objectResult, plainDate, "object: new object");
-TemporalHelpers.assertPlainDate(objectResult, 1976, 11, "M11", 18, "object");
-assert.sameValue(objectResult.getISOFields().calendar, calendar, "object: calendar");
+const calendar = "iso8601";
 
 const stringResult = plainDate.withCalendar("iso8601");
 assert.notSameValue(stringResult, plainDate, "string: new object");
 TemporalHelpers.assertPlainDate(stringResult, 1976, 11, "M11", 18, "string");
 assert.sameValue(stringResult.getISOFields().calendar, "iso8601", "string: calendar slot stores a string");
-
-const originalCalendar = plainDate.getISOFields().calendar;
-const sameResult = plainDate.withCalendar(originalCalendar);
-assert.notSameValue(sameResult, plainDate, "original: new object");
-TemporalHelpers.assertPlainDate(sameResult, 1976, 11, "M11", 18, "original");
-assert.sameValue(sameResult.getISOFields().calendar, originalCalendar, "original: calendar slot stores and object");
diff --git a/test/built-ins/Temporal/PlainDate/prototype/withCalendar/branding.js b/test/built-ins/Temporal/PlainDate/prototype/withCalendar/branding.js
index 964b62ac28..3b25999099 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/withCalendar/branding.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/withCalendar/branding.js
@@ -11,7 +11,7 @@ const withCalendar = Temporal.PlainDate.prototype.withCalendar;
 
 assert.sameValue(typeof withCalendar, "function");
 
-const args = [new Temporal.Calendar("iso8601")];
+const args = ["iso8601"];
 
 assert.throws(TypeError, () => withCalendar.apply(undefined, args), "undefined");
 assert.throws(TypeError, () => withCalendar.apply(null, args), "null");
diff --git a/test/built-ins/Temporal/PlainDateTime/constructor-full.js b/test/built-ins/Temporal/PlainDateTime/constructor-full.js
index c9cd4f5192..ac549099a9 100644
--- a/test/built-ins/Temporal/PlainDateTime/constructor-full.js
+++ b/test/built-ins/Temporal/PlainDateTime/constructor-full.js
@@ -8,8 +8,7 @@ features: [Temporal]
 includes: [temporalHelpers.js]
 ---*/
 
-const calendar = Temporal.Calendar.from("iso8601");
-const datetime = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, calendar);
+const datetime = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, "iso8601");
 
 TemporalHelpers.assertPlainDateTime(datetime,
   1976, 11, "M11", 18, 15, 23, 30, 123, 456, 789,
@@ -18,6 +17,6 @@ TemporalHelpers.assertPlainDateTime(datetime,
 
 assert.sameValue(
   datetime.getISOFields().calendar,
-  calendar,
+  "iso8601",
   "calendar supplied in constructor can be extracted and is unchanged"
 );
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/dayOfWeek/basic.js b/test/built-ins/Temporal/PlainDateTime/prototype/dayOfWeek/basic.js
index 437ac74b60..de897ea3a4 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/dayOfWeek/basic.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/dayOfWeek/basic.js
@@ -7,6 +7,5 @@ description: Checking day of week for a "normal" case (non-undefined, non-bounda
 features: [Temporal]
 ---*/
 
-const calendar = Temporal.Calendar.from("iso8601");
-const datetime = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, calendar);
+const datetime = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, "iso8601");
 assert.sameValue(datetime.dayOfWeek, 4, "check day of week information");
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/dayOfYear/basic.js b/test/built-ins/Temporal/PlainDateTime/prototype/dayOfYear/basic.js
index 98ee0fbef0..3d5735fd42 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/dayOfYear/basic.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/dayOfYear/basic.js
@@ -7,6 +7,5 @@ description: Checking day of year for a "normal" case (non-undefined, non-bounda
 features: [Temporal]
 ---*/
 
-const calendar = Temporal.Calendar.from("iso8601");
-const datetime = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, calendar);
+const datetime = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, "iso8601");
 assert.sameValue(datetime.dayOfYear, 323, "check day of year information");
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/equals/argument-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/PlainDateTime/prototype/equals/argument-propertybag-calendar-wrong-type.js
index 6825ff3d19..b5a21e8622 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/equals/argument-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/equals/argument-propertybag-calendar-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.PlainDateTime(2000, 5, 2, 12, 34, 56, 987, 654, 321);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/monthsInYear/basic.js b/test/built-ins/Temporal/PlainDateTime/prototype/monthsInYear/basic.js
index f918a25355..579b6e619b 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/monthsInYear/basic.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/monthsInYear/basic.js
@@ -7,6 +7,5 @@ description: Checking months in year for a "normal" case (non-undefined, non-bou
 features: [Temporal]
 ---*/
 
-const calendar = Temporal.Calendar.from("iso8601");
-const datetime = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, calendar);
+const datetime = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, "iso8601");
 assert.sameValue(datetime.monthsInYear, 12, "check months in year information");
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/since/argument-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/PlainDateTime/prototype/since/argument-propertybag-calendar-wrong-type.js
index 6e17c616a0..1817dc7ebb 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/since/argument-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/since/argument-propertybag-calendar-wrong-type.js
@@ -9,7 +9,6 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
 const instance = new Temporal.PlainDateTime(2000, 5, 2, 12, 34, 56, 987, 654, 321);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/toString/basic.js b/test/built-ins/Temporal/PlainDateTime/prototype/toString/basic.js
index 5e5b7596a4..2930e0e76e 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/toString/basic.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/toString/basic.js
@@ -7,7 +7,6 @@ description: Checking the string form of an explicitly constructed instance with
 features: [Temporal]
 ---*/
 
-const calendar = Temporal.Calendar.from("iso8601");
-const datetime = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, calendar);
+const datetime = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, "iso8601");
 
 assert.sameValue(datetime.toString(), "1976-11-18T15:23:30.123456789", "check string value");
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/branding.js b/test/built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/branding.js
index d58915e726..47d7efb3aa 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/branding.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/branding.js
@@ -11,7 +11,7 @@ const toZonedDateTime = Temporal.PlainDateTime.prototype.toZonedDateTime;
 
 assert.sameValue(typeof toZonedDateTime, "function");
 
-const args = [new Temporal.TimeZone("UTC")];
+const args = ["UTC"];
 
 assert.throws(TypeError, () => toZonedDateTime.apply(undefined, args), "undefined");
 assert.throws(TypeError, () => toZonedDateTime.apply(null, args), "null");
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/disambiguation-invalid-string.js b/test/built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/disambiguation-invalid-string.js
index ab7127ce59..0c767c50e2 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/disambiguation-invalid-string.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/disambiguation-invalid-string.js
@@ -15,12 +15,11 @@ features: [Temporal]
 ---*/
 
 const datetime = new Temporal.PlainDateTime(2001, 9, 9, 1, 46, 40, 987, 654, 321);
-const timeZone = new Temporal.TimeZone("UTC");
 const invalidStrings = ["obviously bad", "", "EARLIER", "earlıer", "late\u0131r", "reject\0"];
 invalidStrings.forEach((s) => {
   assert.throws(
     RangeError,
-    () => datetime.toZonedDateTime(timeZone, { disambiguation: s }),
+    () => datetime.toZonedDateTime("UTC", { disambiguation: s }),
     `invalid disambiguation string (${s})`);
 });
 
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/disambiguation-wrong-type.js b/test/built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/disambiguation-wrong-type.js
index bf7d4dbb17..86a95283ed 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/disambiguation-wrong-type.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/disambiguation-wrong-type.js
@@ -16,8 +16,7 @@ features: [Temporal]
 ---*/
 
 const datetime = new Temporal.PlainDateTime(2001, 9, 9, 1, 46, 40, 987, 654, 321);
-const timeZone = new Temporal.TimeZone("UTC");
 TemporalHelpers.checkStringOptionWrongType("disambiguation", "compatible",
-  (disambiguation) => datetime.toZonedDateTime(timeZone, { disambiguation }),
+  (disambiguation) => datetime.toZonedDateTime("UTC", { disambiguation }),
   (result, descr) => assert.sameValue(result.epochNanoseconds, 1_000_000_000_987_654_321n, descr),
 );
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/until/argument-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/PlainDateTime/prototype/until/argument-propertybag-calendar-wrong-type.js
index 0f1dd41ef1..42545efbea 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/until/argument-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/until/argument-propertybag-calendar-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.PlainDateTime(2000, 5, 2, 12, 34, 56, 987, 654, 321);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/weekOfYear/basic.js b/test/built-ins/Temporal/PlainDateTime/prototype/weekOfYear/basic.js
index 6273dbc54c..4d8c71fd68 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/weekOfYear/basic.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/weekOfYear/basic.js
@@ -7,6 +7,5 @@ description: Checking week of year for a "normal" case (non-undefined, non-bound
 features: [Temporal]
 ---*/
 
-const calendar = Temporal.Calendar.from("iso8601");
-const datetime = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, calendar);
+const datetime = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, "iso8601");
 assert.sameValue(datetime.weekOfYear, 47, "check week of year information");
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/basic.js b/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/basic.js
index 1f38678c20..ad23448fb5 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/basic.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/basic.js
@@ -9,7 +9,7 @@ includes: [temporalHelpers.js]
 ---*/
 
 const dt = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789);
-const calendar = new Temporal.Calendar("iso8601");
+const calendar = "iso8601";
 
 const result = dt.withCalendar(calendar);
 
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/branding.js b/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/branding.js
index 911f96a77f..7363ee0946 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/branding.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/branding.js
@@ -11,7 +11,7 @@ const withCalendar = Temporal.PlainDateTime.prototype.withCalendar;
 
 assert.sameValue(typeof withCalendar, "function");
 
-const args = [new Temporal.Calendar("iso8601")];
+const args = ["iso8601"];
 
 assert.throws(TypeError, () => withCalendar.apply(undefined, args), "undefined");
 assert.throws(TypeError, () => withCalendar.apply(null, args), "null");
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/yearOfWeek/basic.js b/test/built-ins/Temporal/PlainDateTime/prototype/yearOfWeek/basic.js
index ec1a834b40..41f3aaf453 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/yearOfWeek/basic.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/yearOfWeek/basic.js
@@ -7,6 +7,5 @@ description: Checking yearOfWeek for a "normal" case (non-undefined, non-boundar
 features: [Temporal]
 ---*/
 
-const calendar = Temporal.Calendar.from("iso8601");
-const datetime = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, calendar);
+const datetime = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, "iso8601");
 assert.sameValue(datetime.yearOfWeek, 1976, "check yearOfWeek information");
diff --git a/test/built-ins/Temporal/PlainMonthDay/infinity-throws-rangeerror.js b/test/built-ins/Temporal/PlainMonthDay/infinity-throws-rangeerror.js
index a96544f0bd..c4ba779580 100644
--- a/test/built-ins/Temporal/PlainMonthDay/infinity-throws-rangeerror.js
+++ b/test/built-ins/Temporal/PlainMonthDay/infinity-throws-rangeerror.js
@@ -8,11 +8,9 @@ includes: [compareArray.js, temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const isoCalendar = Temporal.Calendar.from('iso8601');
-
 assert.throws(RangeError, () => new Temporal.PlainMonthDay(Infinity, 1));
 assert.throws(RangeError, () => new Temporal.PlainMonthDay(1, Infinity));
-assert.throws(RangeError, () => new Temporal.PlainMonthDay(1, 1, isoCalendar, Infinity));
+assert.throws(RangeError, () => new Temporal.PlainMonthDay(1, 1, "iso8601", Infinity));
 
 const O = (primitiveValue, propertyName) => (calls) => TemporalHelpers.toPrimitiveObserver(calls, primitiveValue, propertyName);
 const tests = [
diff --git a/test/built-ins/Temporal/PlainMonthDay/negative-infinity-throws-rangeerror.js b/test/built-ins/Temporal/PlainMonthDay/negative-infinity-throws-rangeerror.js
index 1944f9c666..2908e327fb 100644
--- a/test/built-ins/Temporal/PlainMonthDay/negative-infinity-throws-rangeerror.js
+++ b/test/built-ins/Temporal/PlainMonthDay/negative-infinity-throws-rangeerror.js
@@ -8,11 +8,9 @@ includes: [compareArray.js, temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const isoCalendar = Temporal.Calendar.from('iso8601');
-
 assert.throws(RangeError, () => new Temporal.PlainMonthDay(-Infinity, 1));
 assert.throws(RangeError, () => new Temporal.PlainMonthDay(1, -Infinity));
-assert.throws(RangeError, () => new Temporal.PlainMonthDay(1, 1, isoCalendar, -Infinity));
+assert.throws(RangeError, () => new Temporal.PlainMonthDay(1, 1, "iso8601", -Infinity));
 
 const O = (primitiveValue, propertyName) => (calls) => TemporalHelpers.toPrimitiveObserver(calls, primitiveValue, propertyName);
 const tests = [
diff --git a/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-propertybag-calendar-wrong-type.js
index 850d900824..13831fb728 100644
--- a/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-propertybag-calendar-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.PlainMonthDay(5, 2);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/PlainMonthDay/refisoyear-out-of-range.js b/test/built-ins/Temporal/PlainMonthDay/refisoyear-out-of-range.js
index 63e7e9d4e0..4a6e63c73b 100644
--- a/test/built-ins/Temporal/PlainMonthDay/refisoyear-out-of-range.js
+++ b/test/built-ins/Temporal/PlainMonthDay/refisoyear-out-of-range.js
@@ -7,7 +7,5 @@ description: referenceISOYear argument, if given, can cause RangeError
 features: [Temporal]
 ---*/
 
-const calendar = new Temporal.Calendar("iso8601");
-
-assert.throws(RangeError, () => new Temporal.PlainMonthDay(9, 14, calendar, 275760), "after the maximum ISO date");
-assert.throws(RangeError, () => new Temporal.PlainMonthDay(4, 18, calendar, -271821), "before the minimum ISO date")
+assert.throws(RangeError, () => new Temporal.PlainMonthDay(9, 14, "iso8601", 275760), "after the maximum ISO date");
+assert.throws(RangeError, () => new Temporal.PlainMonthDay(4, 18, "iso8601", -271821), "before the minimum ISO date")
diff --git a/test/built-ins/Temporal/PlainMonthDay/refisoyear-undefined.js b/test/built-ins/Temporal/PlainMonthDay/refisoyear-undefined.js
index f9671ba848..062d7d3622 100644
--- a/test/built-ins/Temporal/PlainMonthDay/refisoyear-undefined.js
+++ b/test/built-ins/Temporal/PlainMonthDay/refisoyear-undefined.js
@@ -7,8 +7,7 @@ description: referenceISOYear argument defaults to 1972 if not given
 features: [Temporal]
 ---*/
 
-const calendar = new Temporal.Calendar("iso8601");
-const args = [5, 2, calendar];
+const args = [5, 2, "iso8601"];
 
 const dateExplicit = new Temporal.PlainMonthDay(...args, undefined);
 assert.sameValue(dateExplicit.getISOFields().isoYear, 1972, "default referenceISOYear is 1972");
diff --git a/test/built-ins/Temporal/PlainYearMonth/compare/compare-reference-day.js b/test/built-ins/Temporal/PlainYearMonth/compare/compare-reference-day.js
index 29a9c48661..d7e41068ac 100644
--- a/test/built-ins/Temporal/PlainYearMonth/compare/compare-reference-day.js
+++ b/test/built-ins/Temporal/PlainYearMonth/compare/compare-reference-day.js
@@ -7,7 +7,6 @@ description: compare() takes the reference day into account
 features: [Temporal]
 ---*/
 
-const iso = Temporal.Calendar.from("iso8601");
-const ym1 = new Temporal.PlainYearMonth(2000, 1, iso, 1);
-const ym2 = new Temporal.PlainYearMonth(2000, 1, iso, 2);
+const ym1 = new Temporal.PlainYearMonth(2000, 1, "iso8601", 1);
+const ym2 = new Temporal.PlainYearMonth(2000, 1, "iso8601", 2);
 assert.sameValue(Temporal.PlainYearMonth.compare(ym1, ym2), -1);
diff --git a/test/built-ins/Temporal/PlainYearMonth/infinity-throws-rangeerror.js b/test/built-ins/Temporal/PlainYearMonth/infinity-throws-rangeerror.js
index b81f09b70e..521c631489 100644
--- a/test/built-ins/Temporal/PlainYearMonth/infinity-throws-rangeerror.js
+++ b/test/built-ins/Temporal/PlainYearMonth/infinity-throws-rangeerror.js
@@ -8,11 +8,9 @@ includes: [compareArray.js, temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const isoCalendar = Temporal.Calendar.from('iso8601');
-
 assert.throws(RangeError, () => new Temporal.PlainYearMonth(Infinity, 1));
 assert.throws(RangeError, () => new Temporal.PlainYearMonth(1970, Infinity));
-assert.throws(RangeError, () => new Temporal.PlainYearMonth(1970, 1, isoCalendar, Infinity));
+assert.throws(RangeError, () => new Temporal.PlainYearMonth(1970, 1, "iso8601", Infinity));
 
 const O = (primitiveValue, propertyName) => (calls) => TemporalHelpers.toPrimitiveObserver(calls, primitiveValue, propertyName);
 const tests = [
diff --git a/test/built-ins/Temporal/PlainYearMonth/negative-infinity-throws-rangeerror.js b/test/built-ins/Temporal/PlainYearMonth/negative-infinity-throws-rangeerror.js
index 0f65524ae8..b49d79c077 100644
--- a/test/built-ins/Temporal/PlainYearMonth/negative-infinity-throws-rangeerror.js
+++ b/test/built-ins/Temporal/PlainYearMonth/negative-infinity-throws-rangeerror.js
@@ -8,11 +8,10 @@ includes: [compareArray.js, temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const isoCalendar = Temporal.Calendar.from('iso8601');
 
 assert.throws(RangeError, () => new Temporal.PlainYearMonth(-Infinity, 1));
 assert.throws(RangeError, () => new Temporal.PlainYearMonth(1970, -Infinity));
-assert.throws(RangeError, () => new Temporal.PlainYearMonth(1970, 1, isoCalendar, -Infinity));
+assert.throws(RangeError, () => new Temporal.PlainYearMonth(1970, 1, "iso8601", -Infinity));
 
 const O = (primitiveValue, propertyName) => (calls) => TemporalHelpers.toPrimitiveObserver(calls, primitiveValue, propertyName);
 const tests = [
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-propertybag-calendar-wrong-type.js
index e55cb3cee8..9b37beb412 100644
--- a/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-propertybag-calendar-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.PlainYearMonth(2000, 5);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/equals/compare-reference-day.js b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/compare-reference-day.js
index 3c40f5031e..8cf550fa4b 100644
--- a/test/built-ins/Temporal/PlainYearMonth/prototype/equals/compare-reference-day.js
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/compare-reference-day.js
@@ -7,7 +7,6 @@ description: equals() takes the reference day into account
 features: [Temporal]
 ---*/
 
-const iso = Temporal.Calendar.from("iso8601");
-const ym1 = new Temporal.PlainYearMonth(2000, 1, iso, 1);
-const ym2 = new Temporal.PlainYearMonth(2000, 1, iso, 2);
+const ym1 = new Temporal.PlainYearMonth(2000, 1, "iso8601", 1);
+const ym2 = new Temporal.PlainYearMonth(2000, 1, "iso8601", 2);
 assert.sameValue(ym1.equals(ym2), false);
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-propertybag-calendar-wrong-type.js
index 1368ad4ebd..4ed5d1450d 100644
--- a/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-propertybag-calendar-wrong-type.js
@@ -9,7 +9,6 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
 const instance = new Temporal.PlainYearMonth(2000, 5);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-propertybag-calendar-wrong-type.js
index e26fb72820..f83308449a 100644
--- a/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-propertybag-calendar-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.PlainYearMonth(2000, 5);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/PlainYearMonth/refisoday-undefined.js b/test/built-ins/Temporal/PlainYearMonth/refisoday-undefined.js
index 95496c7764..3172cdb86f 100644
--- a/test/built-ins/Temporal/PlainYearMonth/refisoday-undefined.js
+++ b/test/built-ins/Temporal/PlainYearMonth/refisoday-undefined.js
@@ -7,8 +7,7 @@ description: referenceISODay argument defaults to 1 if not given
 features: [Temporal]
 ---*/
 
-const calendar = new Temporal.Calendar("iso8601");
-const args = [2000, 5, calendar];
+const args = [2000, 5];
 
 const dateExplicit = new Temporal.PlainYearMonth(...args, undefined);
 assert.sameValue(dateExplicit.getISOFields().isoDay, 1, "default referenceISODay is 1");
diff --git a/test/built-ins/Temporal/ZonedDateTime/calendar-undefined.js b/test/built-ins/Temporal/ZonedDateTime/calendar-undefined.js
index 0de531db8a..6851efd813 100644
--- a/test/built-ins/Temporal/ZonedDateTime/calendar-undefined.js
+++ b/test/built-ins/Temporal/ZonedDateTime/calendar-undefined.js
@@ -7,13 +7,13 @@ description: Calendar argument defaults to the built-in ISO 8601 calendar
 features: [BigInt, Temporal]
 ---*/
 
-const args = [957270896987654321n, new Temporal.TimeZone("UTC")];
 
 Object.defineProperty(Temporal.Calendar, "from", {
   get() {
     throw new Test262Error("Should not get Calendar.from");
   },
 });
+const args = [957270896987654321n, "UTC"];
 
 const explicit = new Temporal.ZonedDateTime(...args, undefined);
 assert.sameValue(explicit.getISOFields().calendar, "iso8601", "calendar slot should store a string");
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-case-insensitive.js
index ca19916005..5642ae718a 100644
--- a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-case-insensitive.js
@@ -7,7 +7,7 @@ description: The calendar name is case-insensitive
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const datetime = new Temporal.ZonedDateTime(0n, timeZone);
 
 const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar: "IsO8601" };
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-leap-second.js
index 0bf607c323..a9671e128a 100644
--- a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-leap-second.js
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-leap-second.js
@@ -7,7 +7,7 @@ description: Leap second is a valid ISO string for a calendar in a property bag
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const datetime = new Temporal.ZonedDateTime(217_123_200_000_000_000n, timeZone);
 const calendar = "2016-12-31T23:59:60+00:00[UTC]";
 
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-number.js b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-number.js
index e01d722949..c681c39c30 100644
--- a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-number.js
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-number.js
@@ -7,7 +7,7 @@ description: A number as calendar in a property bag is not accepted
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const datetime = new Temporal.ZonedDateTime(0n, timeZone);
 
 const numbers = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-string.js b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-string.js
index d0208d5419..7918945d00 100644
--- a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-string.js
@@ -19,7 +19,7 @@ Object.defineProperty(Temporal.Calendar.prototype, "dateFromFields", {
 
 const calendar = "iso8601";
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const datetime = new Temporal.ZonedDateTime(0n, timeZone);
 const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar };
 
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-wrong-type.js
index 3641ce8f63..a7093dae20 100644
--- a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-wrong-type.js
@@ -5,11 +5,11 @@
 esid: sec-temporal.zoneddatetime.compare
 description: >
   Appropriate error thrown when a calendar property from a property bag cannot
-  be converted to a calendar object or string
+  be converted to a calendar ID
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const datetime = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("UTC"));
+const datetime = new Temporal.ZonedDateTime(0n, "UTC");
 
 const primitiveTests = [
   [null, "null"],
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-year-zero.js b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-year-zero.js
index 26a1253b18..cb98229a28 100644
--- a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-year-zero.js
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-year-zero.js
@@ -7,7 +7,7 @@ description: Negative zero, as an extended year, is rejected
 features: [Temporal, arrow-function]
 ---*/
 
-const datetime = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("UTC"));
+const datetime = new Temporal.ZonedDateTime(0n, "UTC");
 const invalidStrings = [
   "-000000-10-31",
   "-000000-10-31T17:45",
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-invalid-offset-string.js b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-invalid-offset-string.js
index 63baaa1af7..3d16895806 100644
--- a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-invalid-offset-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-invalid-offset-string.js
@@ -7,7 +7,7 @@ description: Property bag with offset property is rejected if offset is in the w
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const datetime = new Temporal.ZonedDateTime(1_000_000_000_987_654_321n, timeZone);
 
 const badOffsets = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-offset-not-agreeing-with-timezone.js b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-offset-not-agreeing-with-timezone.js
index 79f6346c1f..7dd409de6c 100644
--- a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-offset-not-agreeing-with-timezone.js
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-offset-not-agreeing-with-timezone.js
@@ -7,7 +7,7 @@ description: Property bag with offset property is rejected if offset does not ag
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("+01:00");
+const timeZone = "+01:00";
 const datetime = new Temporal.ZonedDateTime(0n, timeZone);
 
 const properties = { year: 2021, month: 10, day: 28, offset: "-07:00", timeZone };
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-timezone-string-year-zero.js b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-timezone-string-year-zero.js
index b5a4de63df..6c9e55b6cd 100644
--- a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-timezone-string-year-zero.js
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-timezone-string-year-zero.js
@@ -7,7 +7,7 @@ description: Negative zero, as an extended year, is rejected
 features: [Temporal, arrow-function]
 ---*/
 
-const datetime = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("UTC"));
+const datetime = new Temporal.ZonedDateTime(0n, "UTC");
 const invalidStrings = [
   "-000000-10-31T17:45Z",
   "-000000-10-31T17:45+00:00[UTC]",
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-timezone-string.js b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-timezone-string.js
index e5f1be57ff..60b84e507c 100644
--- a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-timezone-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-timezone-string.js
@@ -26,7 +26,7 @@ Object.defineProperty(Temporal.TimeZone.prototype, "getOffsetNanosecondsFor", {
 });
 
 ["UTC", "+01:30"].forEach((timeZone) => {
-  const epoch = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone(timeZone));
+  const epoch = new Temporal.ZonedDateTime(0n, timeZone);
 
   // These should be valid input and not throw
   Temporal.ZonedDateTime.compare({ year: 2020, month: 5, day: 2, timeZone }, epoch);
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-timezone-wrong-type.js b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-timezone-wrong-type.js
index 7c6ec7d0ef..78ee6ad600 100644
--- a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-timezone-wrong-type.js
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-timezone-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const datetime = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("UTC"));
+const datetime = new Temporal.ZonedDateTime(0n, "UTC");
 
 const primitiveTests = [
   [null, "null"],
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/argument-wrong-type.js b/test/built-ins/Temporal/ZonedDateTime/compare/argument-wrong-type.js
index 6e8600fdaf..3cb808a6bb 100644
--- a/test/built-ins/Temporal/ZonedDateTime/compare/argument-wrong-type.js
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/argument-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const other = new Temporal.ZonedDateTime(0n, timeZone);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/leap-second.js b/test/built-ins/Temporal/ZonedDateTime/compare/leap-second.js
index cdd1368336..c2783a7396 100644
--- a/test/built-ins/Temporal/ZonedDateTime/compare/leap-second.js
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/leap-second.js
@@ -7,7 +7,7 @@ description: Leap second is a valid ISO string for ZonedDateTime
 features: [Temporal]
 ---*/
 
-const datetime = new Temporal.ZonedDateTime(1_483_228_799_000_000_000n, new Temporal.TimeZone("UTC"));
+const datetime = new Temporal.ZonedDateTime(1_483_228_799_000_000_000n, "UTC");
 
 let arg = "2016-12-31T23:59:60+00:00[UTC]";
 const result1 = Temporal.ZonedDateTime.compare(arg, datetime);
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-case-insensitive.js
index 3baa8ff31f..fb3ce13833 100644
--- a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-case-insensitive.js
@@ -7,7 +7,7 @@ description: The calendar name is case-insensitive
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar: "IsO8601" };
 const result = Temporal.ZonedDateTime.from(arg);
 assert.sameValue(result.calendarId, "iso8601", "Calendar is case-insensitive");
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-iso-string.js b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-iso-string.js
index f26955131d..5e2cabddc8 100644
--- a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-iso-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-iso-string.js
@@ -17,7 +17,7 @@ for (const calendar of [
   "2020-01",
   "2020-01[u-ca=iso8601]",
 ]) {
-  const timeZone = new Temporal.TimeZone("UTC");
+  const timeZone = "UTC";
 const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar };
   const result = Temporal.ZonedDateTime.from(arg);
   assert.sameValue(result.calendarId, "iso8601", `Calendar created from string "${calendar}"`);
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-leap-second.js
index 338a162ad5..a31b570f8f 100644
--- a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-leap-second.js
+++ b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-leap-second.js
@@ -7,7 +7,7 @@ description: Leap second is a valid ISO string for a calendar in a property bag
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const calendar = "2016-12-31T23:59:60+00:00[UTC]";
 
 const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar };
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-number.js b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-number.js
index fc9dbcb170..97dc4d646f 100644
--- a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-number.js
+++ b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-number.js
@@ -6,8 +6,7 @@ esid: sec-temporal.zoneddatetime.from
 description: A number as calendar in a property bag is not accepted
 features: [Temporal]
 ---*/
-
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 
 const numbers = [
   1,
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-string.js b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-string.js
index c9d1b7bddb..d2f252e72d 100644
--- a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-string.js
@@ -9,7 +9,7 @@ features: [Temporal]
 
 const calendar = "iso8601";
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar };
 const result = Temporal.ZonedDateTime.from(arg);
 assert.sameValue(result.calendarId, "iso8601", `Calendar created from string "${calendar}"`);
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-invalid-offset-string.js b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-invalid-offset-string.js
index daf623d3b0..9603bda486 100644
--- a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-invalid-offset-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-invalid-offset-string.js
@@ -7,7 +7,7 @@ description: Property bag with offset property is rejected if offset is in the w
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 
 const offsetOptions = ['use', 'prefer', 'ignore', 'reject'];
 
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-offset-not-agreeing-with-timezone.js b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-offset-not-agreeing-with-timezone.js
index 4bce6c887d..4f82b9a08a 100644
--- a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-offset-not-agreeing-with-timezone.js
+++ b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-offset-not-agreeing-with-timezone.js
@@ -7,7 +7,7 @@ description: Property bag with offset property is rejected if offset does not ag
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("+01:00");
+const timeZone = "+01:00";
 
 const properties = { year: 2021, month: 10, day: 28, offset: "-07:00", timeZone };
 assert.throws(RangeError, () => Temporal.ZonedDateTime.from(properties), "offset property not matching time zone is rejected");
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/argument-zoneddatetime.js b/test/built-ins/Temporal/ZonedDateTime/from/argument-zoneddatetime.js
index d1452483ce..b8b669175d 100644
--- a/test/built-ins/Temporal/ZonedDateTime/from/argument-zoneddatetime.js
+++ b/test/built-ins/Temporal/ZonedDateTime/from/argument-zoneddatetime.js
@@ -7,7 +7,7 @@ description: A ZonedDateTime object is copied, not returned directly
 features: [Temporal]
 ---*/
 
-const orig = new Temporal.ZonedDateTime(946684800_000_000_010n, new Temporal.TimeZone("UTC"));
+const orig = new Temporal.ZonedDateTime(946684800_000_000_010n, "UTC");
 const result = Temporal.ZonedDateTime.from(orig);
 
 assert.sameValue(result.epochNanoseconds, 946684800_000_000_010n, "ZonedDateTime is copied");
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/disambiguation-invalid-string.js b/test/built-ins/Temporal/ZonedDateTime/from/disambiguation-invalid-string.js
index b9529653e0..31eefbda2e 100644
--- a/test/built-ins/Temporal/ZonedDateTime/from/disambiguation-invalid-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/from/disambiguation-invalid-string.js
@@ -24,6 +24,5 @@ features: [Temporal]
 const datetime = new Temporal.ZonedDateTime(1_000_000_000_987_654_321n, "UTC");
 assert.throws(RangeError, () => Temporal.ZonedDateTime.from(datetime, { disambiguation: "other string" }));
 
-const timeZone = new Temporal.TimeZone("UTC");
-const propertyBag = { timeZone, year: 2001, month: 9, day: 9, hour: 1, minute: 46, second: 40, millisecond: 987, microsecond: 654, nanosecond: 321 };
+const propertyBag = { timeZone: "UTC", year: 2001, month: 9, day: 9, hour: 1, minute: 46, second: 40, millisecond: 987, microsecond: 654, nanosecond: 321 };
 assert.throws(RangeError, () => Temporal.ZonedDateTime.from(propertyBag, { disambiguation: "other string" }));
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/disambiguation-wrong-type.js b/test/built-ins/Temporal/ZonedDateTime/from/disambiguation-wrong-type.js
index f997510dc8..842c3afa4e 100644
--- a/test/built-ins/Temporal/ZonedDateTime/from/disambiguation-wrong-type.js
+++ b/test/built-ins/Temporal/ZonedDateTime/from/disambiguation-wrong-type.js
@@ -28,8 +28,7 @@ TemporalHelpers.checkStringOptionWrongType("disambiguation", "compatible",
   (result, descr) => assert.sameValue(result.epochNanoseconds, 1_000_000_000_987_654_321n, descr),
 );
 
-const timeZone = new Temporal.TimeZone("UTC");
-const propertyBag = { timeZone, year: 2001, month: 9, day: 9, hour: 1, minute: 46, second: 40, millisecond: 987, microsecond: 654, nanosecond: 321 };
+const propertyBag = { timeZone: "UTC", year: 2001, month: 9, day: 9, hour: 1, minute: 46, second: 40, millisecond: 987, microsecond: 654, nanosecond: 321 };
 TemporalHelpers.checkStringOptionWrongType("disambiguation", "compatible",
   (disambiguation) => Temporal.ZonedDateTime.from(propertyBag, { disambiguation }),
   (result, descr) => assert.sameValue(result.epochNanoseconds, 1_000_000_000_987_654_321n, descr),
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/offset-invalid-string.js b/test/built-ins/Temporal/ZonedDateTime/from/offset-invalid-string.js
index 730cbc0147..588e469f1f 100644
--- a/test/built-ins/Temporal/ZonedDateTime/from/offset-invalid-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/from/offset-invalid-string.js
@@ -23,6 +23,5 @@ features: [Temporal]
 const datetime = new Temporal.ZonedDateTime(1_000_000_000_987_654_321n, "UTC");
 assert.throws(RangeError, () => Temporal.ZonedDateTime.from(datetime, { offset: "other string" }));
 
-const timeZone = new Temporal.TimeZone("UTC");
-const propertyBag = { timeZone, year: 2001, month: 9, day: 9, hour: 1, minute: 46, second: 40, millisecond: 987, microsecond: 654, nanosecond: 321 };
+const propertyBag = { timeZone: "UTC", year: 2001, month: 9, day: 9, hour: 1, minute: 46, second: 40, millisecond: 987, microsecond: 654, nanosecond: 321 };
 assert.throws(RangeError, () => Temporal.ZonedDateTime.from(propertyBag, { offset: "other string" }));
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/offset-undefined.js b/test/built-ins/Temporal/ZonedDateTime/from/offset-undefined.js
index 1939303ec0..a3c67e1b52 100644
--- a/test/built-ins/Temporal/ZonedDateTime/from/offset-undefined.js
+++ b/test/built-ins/Temporal/ZonedDateTime/from/offset-undefined.js
@@ -20,8 +20,7 @@ info: |
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("-04:00");
-const propertyBag = { timeZone, offset: "+01:00", year: 2020, month: 2, day: 16, hour: 23, minute: 45 };
+const propertyBag = { timeZone: "-04:00", offset: "+01:00", year: 2020, month: 2, day: 16, hour: 23, minute: 45 };
 
 assert.throws(RangeError, () => Temporal.ZonedDateTime.from(propertyBag, { offset: undefined }), "default offset is reject");
 // See options-undefined.js for {}
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/offset-wrong-type.js b/test/built-ins/Temporal/ZonedDateTime/from/offset-wrong-type.js
index 5c5bc1f70c..6c3df817ed 100644
--- a/test/built-ins/Temporal/ZonedDateTime/from/offset-wrong-type.js
+++ b/test/built-ins/Temporal/ZonedDateTime/from/offset-wrong-type.js
@@ -27,8 +27,7 @@ TemporalHelpers.checkStringOptionWrongType("offset", "reject",
   (result, descr) => assert.sameValue(result.epochNanoseconds, 1_000_000_000_987_654_321n, descr),
 );
 
-const timeZone = new Temporal.TimeZone("UTC");
-const propertyBag = { timeZone, offset: "+00:00", year: 2001, month: 9, day: 9, hour: 1, minute: 46, second: 40, millisecond: 987, microsecond: 654, nanosecond: 321 };
+const propertyBag = { timeZone: "UTC", offset: "+00:00", year: 2001, month: 9, day: 9, hour: 1, minute: 46, second: 40, millisecond: 987, microsecond: 654, nanosecond: 321 };
 TemporalHelpers.checkStringOptionWrongType("offset", "reject",
   (offset) => Temporal.ZonedDateTime.from(propertyBag, { offset }),
   (result, descr) => assert.sameValue(result.epochNanoseconds, 1_000_000_000_987_654_321n, descr),
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-case-insensitive.js
index fe11b2b851..e4b80cb513 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-case-insensitive.js
@@ -7,7 +7,7 @@ description: The calendar name is case-insensitive
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar: "IsO8601" };
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-iso-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-iso-string.js
index 3012fc4a3b..5b754d6a3d 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-iso-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-iso-string.js
@@ -7,7 +7,7 @@ description: An ISO 8601 string can be converted to a calendar ID in Calendar
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 for (const calendar of [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-leap-second.js
index 43fca0aa85..e1f96d3e0a 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-leap-second.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-leap-second.js
@@ -7,7 +7,7 @@ description: Leap second is a valid ISO string for a calendar in a property bag
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const calendar = "2016-12-31T23:59:60+00:00[UTC]";
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-number.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-number.js
index 06248b267f..a975129dfb 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-number.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-number.js
@@ -7,7 +7,7 @@ description: A number as calendar in a property bag is not accepted
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const numbers = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-string.js
index f9d8641d73..c36e2a675f 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-string.js
@@ -7,7 +7,7 @@ description: A calendar ID is valid input for Calendar
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const calendar = "iso8601";
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-wrong-type.js
index 794e1d6125..8eddd1de7d 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-wrong-type.js
@@ -5,11 +5,11 @@
 esid: sec-temporal.zoneddatetime.prototype.equals
 description: >
   Appropriate error thrown when a calendar property from a property bag cannot
-  be converted to a calendar object or string
+  be converted to a calendar ID
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-year-zero.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-year-zero.js
index dd1eae6d6a..c6d9dae35c 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-year-zero.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-year-zero.js
@@ -14,7 +14,7 @@ const invalidStrings = [
   "-000000-10-31T17:45+01:00",
   "-000000-10-31T17:45+00:00[UTC]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach((str) => {
   const arg = { year: 1976, month: 11, day: 18, calendar: str };
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-invalid-offset-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-invalid-offset-string.js
index 18538ce5ab..0ca261212f 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-invalid-offset-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-invalid-offset-string.js
@@ -7,7 +7,7 @@ description: Property bag with offset property is rejected if offset is in the w
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const badOffsets = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-offset-not-agreeing-with-timezone.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-offset-not-agreeing-with-timezone.js
index 2605577967..72bbf07005 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-offset-not-agreeing-with-timezone.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-offset-not-agreeing-with-timezone.js
@@ -7,7 +7,7 @@ description: Property bag with offset property is rejected if offset does not ag
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("+01:00");
+const timeZone = "+01:00";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const properties = { year: 2021, month: 10, day: 28, offset: "-07:00", timeZone };
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-string-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-string-leap-second.js
index 4095674ad2..1ce2e31113 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-string-leap-second.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-string-leap-second.js
@@ -7,7 +7,7 @@ description: Leap second is a valid ISO string for TimeZone
 features: [Temporal]
 ---*/
 
-const instance = new Temporal.ZonedDateTime(1588377600_000_000_000n, new Temporal.TimeZone("UTC"));
+const instance = new Temporal.ZonedDateTime(1588377600_000_000_000n, "UTC");
 let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
 
 assert(instance.equals({ year: 2020, month: 5, day: 2, timeZone }), "leap second is a valid ISO string for TimeZone");
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-string-year-zero.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-string-year-zero.js
index 54780e6540..c83c6562e8 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-string-year-zero.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-string-year-zero.js
@@ -11,7 +11,7 @@ const invalidStrings = [
   "-000000-10-31T17:45Z",
   "-000000-10-31T17:45+00:00[UTC]",
 ];
-const instance = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("UTC"));
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 invalidStrings.forEach((timeZone) => {
   assert.throws(
     RangeError,
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-string.js
index 57de6c0244..5925d5a045 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-string.js
@@ -25,10 +25,10 @@ Object.defineProperty(Temporal.TimeZone.prototype, "getOffsetNanosecondsFor", {
   },
 });
 
-const instance1 = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("UTC"));
+const instance1 = new Temporal.ZonedDateTime(0n, "UTC");
 assert(instance1.equals({ year: 1970, month: 1, day: 1, timeZone: "UTC" }), "Time zone created from string 'UTC'");
 
-const instance2 = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("-01:30"));
+const instance2 = new Temporal.ZonedDateTime(0n, "-01:30");
 assert(instance2.equals({ year: 1969, month: 12, day: 31, hour: 22, minute: 30, timeZone: "-01:30" }), "Time zone created from string '-01:30'");
 
 Object.defineProperty(Temporal.TimeZone.prototype, "getPossibleInstantsFor", getPossibleInstantsForOriginal);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-wrong-type.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-wrong-type.js
index 5f8aa22f5e..494a7414b7 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-wrong-type.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-wrong-type.js
@@ -5,11 +5,11 @@
 esid: sec-temporal.zoneddatetime.prototype.equals
 description: >
   Appropriate error thrown when argument cannot be converted to a valid string
-  or object for TimeZone
+  for time zone
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const instance = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("UTC"));
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 
 const primitiveTests = [
   [null, "null"],
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-calendar-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-calendar-annotation.js
index 72352bbc3b..c724776955 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-calendar-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-calendar-annotation.js
@@ -13,8 +13,7 @@ const tests = [
   ["1970-01-01T00:00[UTC][u-ca=iso8601][u-ca=discord]", "second annotation ignored"],
 ];
 
-const timeZone = new Temporal.TimeZone("UTC");
-const instance = new Temporal.ZonedDateTime(0n, timeZone);
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 
 tests.forEach(([arg, description]) => {
   const result = instance.equals(arg);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-critical-unknown-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-critical-unknown-annotation.js
index c1fcd5403a..08e2e68651 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-critical-unknown-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-critical-unknown-annotation.js
@@ -13,8 +13,7 @@ const invalidStrings = [
   "1970-01-01T00:00[UTC][u-ca=iso8601][!foo=bar]",
   "1970-01-01T00:00[foo=bar][!_foo-bar0=Dont-Ignore-This-99999999999]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
-const instance = new Temporal.ZonedDateTime(0n, timeZone);
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 invalidStrings.forEach((arg) => {
   assert.throws(
     RangeError,
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-date-with-utc-offset.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-date-with-utc-offset.js
index 6892a97105..6062e4df27 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-date-with-utc-offset.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-date-with-utc-offset.js
@@ -7,8 +7,7 @@ description: UTC offset not valid with format that does not include a time
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
-const instance = new Temporal.ZonedDateTime(0n, timeZone);
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 
 const validStrings = [
   "1970-01-01T00Z[UTC]",
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-multiple-calendar.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-multiple-calendar.js
index 7627303897..2826b7f24a 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-multiple-calendar.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-multiple-calendar.js
@@ -14,8 +14,7 @@ const invalidStrings = [
   "1970-01-01T00:00[UTC][!u-ca=iso8601][u-ca=iso8601]",
   "1970-01-01T00:00[UTC][u-ca=iso8601][foo=bar][!u-ca=iso8601]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
-const instance = new Temporal.ZonedDateTime(0n, timeZone);
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 invalidStrings.forEach((arg) => {
   assert.throws(
     RangeError,
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-multiple-time-zone.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-multiple-time-zone.js
index 642bb280c2..b33bf53fd1 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-multiple-time-zone.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-multiple-time-zone.js
@@ -14,8 +14,7 @@ const invalidStrings = [
   "1970-01-01T00:00[UTC][u-ca=iso8601][UTC]",
   "1970-01-01T00:00[UTC][foo=bar][UTC]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
-const instance = new Temporal.ZonedDateTime(0n, timeZone);
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 invalidStrings.forEach((arg) => {
   assert.throws(
     RangeError,
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-time-separators.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-time-separators.js
index 3c5f4f802a..fc8d5a4032 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-time-separators.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-time-separators.js
@@ -13,8 +13,7 @@ const tests = [
   ["1970-01-01 00:00+00:00[UTC]", "space between date and time"],
 ];
 
-const timeZone = new Temporal.TimeZone("UTC");
-const instance = new Temporal.ZonedDateTime(0n, timeZone);
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 
 tests.forEach(([arg, description]) => {
   const result = instance.equals(arg);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-time-zone-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-time-zone-annotation.js
index 3de8846476..871fae193c 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-time-zone-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-time-zone-annotation.js
@@ -23,8 +23,7 @@ const tests = [
 ];
 
 tests.forEach(([arg, expectedZone, description]) => {
-  const timeZone = new Temporal.TimeZone(expectedZone);
-  const instance = new Temporal.ZonedDateTime(0n, timeZone);
+  const instance = new Temporal.ZonedDateTime(0n, expectedZone);
   const result = instance.equals(arg);
 
   assert.sameValue(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-unknown-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-unknown-annotation.js
index eb815b4d71..5b1b95123b 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-unknown-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-unknown-annotation.js
@@ -14,8 +14,7 @@ const tests = [
   ["1970-01-01T00:00[UTC][foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
 ];
 
-const timeZone = new Temporal.TimeZone("UTC");
-const instance = new Temporal.ZonedDateTime(0n, timeZone);
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 
 tests.forEach(([arg, description]) => {
   const result = instance.equals(arg);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-wrong-type.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-wrong-type.js
index 4cf570fd74..e3170621ff 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-wrong-type.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/branding.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/branding.js
index 3d135a3d38..aad00b4013 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/branding.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/branding.js
@@ -11,7 +11,7 @@ const equals = Temporal.ZonedDateTime.prototype.equals;
 
 assert.sameValue(typeof equals, "function");
 
-const args = [new Temporal.ZonedDateTime(123456n, new Temporal.TimeZone("UTC"))];
+const args = [new Temporal.ZonedDateTime(123456n, "UTC")];
 
 assert.throws(TypeError, () => equals.apply(undefined, args), "undefined");
 assert.throws(TypeError, () => equals.apply(null, args), "null");
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/leap-second.js
index cc57129d4e..2363650929 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/leap-second.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/leap-second.js
@@ -7,7 +7,7 @@ description: Leap second is a valid ISO string for ZonedDateTime
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(1_483_228_799_000_000_000n, timeZone);
 
 let arg = "2016-12-31T23:59:60+00:00[UTC]";
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/year-zero.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/year-zero.js
index 3e87ae8893..6fd3a52368 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/year-zero.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/year-zero.js
@@ -12,8 +12,7 @@ const invalidStrings = [
   "-0000000-01-01T00:02+00:00[UTC]",
   "-0000000-01-01T00:02:00.000000000+00:00[UTC]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
-const instance = new Temporal.ZonedDateTime(0n, timeZone);
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 invalidStrings.forEach((arg) => {
   assert.throws(
     RangeError,
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/zoneddatetime-string-multiple-offsets.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/zoneddatetime-string-multiple-offsets.js
index 72686fb969..f0044989a0 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/zoneddatetime-string-multiple-offsets.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/zoneddatetime-string-multiple-offsets.js
@@ -7,7 +7,7 @@ description: Sub-minute offset trailing zeroes allowed in ISO string but not in
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("+01:35");
+const timeZone = "+01:35";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 let str = "1970-01-01T01:35:30+01:35:00.000000000[+01:35]";
 
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/zoneddatetime-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/zoneddatetime-string.js
index 68202ab8b8..9a7e7f4f96 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/zoneddatetime-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/zoneddatetime-string.js
@@ -7,7 +7,7 @@ description: Conversion of ISO date-time strings to Temporal.ZonedDateTime insta
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("+01:00");
+const timeZone = "+01:00";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 let str = "1970-01-01T00:00";
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/getISOFields/negative-epochnanoseconds.js b/test/built-ins/Temporal/ZonedDateTime/prototype/getISOFields/negative-epochnanoseconds.js
index 7a4350cecc..93a14d3483 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/getISOFields/negative-epochnanoseconds.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/getISOFields/negative-epochnanoseconds.js
@@ -13,16 +13,14 @@ features: [Temporal]
 includes: [deepEqual.js]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
-const calendar = new Temporal.Calendar("iso8601");
-const datetime = new Temporal.ZonedDateTime(-13849764_999_999_999n, timeZone, calendar);
+const datetime = new Temporal.ZonedDateTime(-13849764_999_999_999n, "UTC");
 
 // This code path shows up anywhere we convert an exact time, before the Unix
 // epoch, with nonzero microseconds or nanoseconds, into a wall time.
 
 const result = datetime.getISOFields();
 assert.deepEqual(result, {
-  calendar,
+  calendar: "iso8601",
   isoDay: 24,
   isoHour: 16,
   isoMicrosecond: 0,
@@ -33,5 +31,5 @@ assert.deepEqual(result, {
   isoSecond: 35,
   isoYear: 1969,
   offset: "+00:00",
-  timeZone,
+  timeZone: "UTC"
 });
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/getISOFields/offset.js b/test/built-ins/Temporal/ZonedDateTime/prototype/getISOFields/offset.js
index 96fa20c61f..45924564a7 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/getISOFields/offset.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/getISOFields/offset.js
@@ -8,8 +8,7 @@ features: [BigInt, Temporal]
 ---*/
 
 function test(timeZoneIdentifier, expectedOffsetString, description) {
-  const timeZone = new Temporal.TimeZone(timeZoneIdentifier);
-  const datetime = new Temporal.ZonedDateTime(0n, timeZone);
+  const datetime = new Temporal.ZonedDateTime(0n, timeZoneIdentifier);
   const fields = datetime.getISOFields();
   assert.sameValue(fields.offset, expectedOffsetString, description);
 }
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/offset/basic.js b/test/built-ins/Temporal/ZonedDateTime/prototype/offset/basic.js
index 6c104323ed..16d2ddb3bf 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/offset/basic.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/offset/basic.js
@@ -8,8 +8,7 @@ features: [BigInt, Temporal]
 ---*/
 
 function test(timeZoneIdentifier, expectedOffsetString, description) {
-  const timeZone = new Temporal.TimeZone(timeZoneIdentifier);
-  const datetime = new Temporal.ZonedDateTime(0n, timeZone);
+  const datetime = new Temporal.ZonedDateTime(0n, timeZoneIdentifier);
   assert.sameValue(datetime.offset, expectedOffsetString, description);
 }
 
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-case-insensitive.js
index bc37379656..c9ff89c434 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-case-insensitive.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar: "IsO8601" };
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-iso-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-iso-string.js
index 8d6e9b9e09..57cd4b962e 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-iso-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-iso-string.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 for (const calendar of [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-leap-second.js
index c2c39d97de..3b428fc2ac 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-leap-second.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-leap-second.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const calendar = "2016-12-31T23:59:60+00:00[UTC]";
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-number.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-number.js
index 7b318fbf4d..49ce7c5ad9 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-number.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-number.js
@@ -7,7 +7,7 @@ description: A number as calendar in a property bag is not accepted
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const numbers = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-string.js
index ba81bd841d..bf1138e0b1 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-string.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const calendar = "iso8601";
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-wrong-type.js
index 7b9aa6dccf..b07b2a3880 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-year-zero.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-year-zero.js
index 5c294a5373..d6ea39cb34 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-year-zero.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-year-zero.js
@@ -14,7 +14,7 @@ const invalidStrings = [
   "-000000-10-31T17:45+01:00",
   "-000000-10-31T17:45+00:00[UTC]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach((str) => {
   const arg = { year: 1976, month: 11, day: 18, calendar: str };
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-invalid-offset-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-invalid-offset-string.js
index 8aa2efceb5..5ac866e413 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-invalid-offset-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-invalid-offset-string.js
@@ -7,7 +7,7 @@ description: Property bag with offset property is rejected if offset is in the w
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const badOffsets = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-offset-not-agreeing-with-timezone.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-offset-not-agreeing-with-timezone.js
index e7c2b3fe33..97b1b07cef 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-offset-not-agreeing-with-timezone.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-offset-not-agreeing-with-timezone.js
@@ -7,7 +7,7 @@ description: Property bag with offset property is rejected if offset does not ag
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("+01:00");
+const timeZone = "+01:00";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const properties = { year: 2021, month: 10, day: 28, offset: "-07:00", timeZone };
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-timezone-string-year-zero.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-timezone-string-year-zero.js
index 27e043ae0e..4f2dce8ab4 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-timezone-string-year-zero.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-timezone-string-year-zero.js
@@ -11,7 +11,7 @@ const invalidStrings = [
   "-000000-10-31T17:45Z",
   "-000000-10-31T17:45+00:00[UTC]",
 ];
-const instance = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("UTC"));
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 invalidStrings.forEach((timeZone) => {
   assert.throws(
     RangeError,
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-timezone-wrong-type.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-timezone-wrong-type.js
index 5278a935d7..ae7a2324f8 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-timezone-wrong-type.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-timezone-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const instance = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("UTC"));
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 
 const primitiveTests = [
   [null, "null"],
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-calendar-annotation-invalid-key.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-calendar-annotation-invalid-key.js
index c1705471d4..444b8c473a 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-calendar-annotation-invalid-key.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-calendar-annotation-invalid-key.js
@@ -12,7 +12,7 @@ const invalidStrings = [
   ["1970-01-01T00:00[UTC][u-CA=iso8601]", "invalid partially-capitalized key"],
   ["1970-01-01T00:00[UTC][FOO=bar]", "invalid capitalized unrecognized key"],
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach(([arg, descr]) => {
   assert.throws(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-calendar-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-calendar-annotation.js
index 575382d8ed..e86d3f5b5e 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-calendar-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-calendar-annotation.js
@@ -14,7 +14,7 @@ const tests = [
   ["1970-01-01T00:00[UTC][u-ca=iso8601][u-ca=discord]", "second annotation ignored"],
 ];
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 tests.forEach(([arg, description]) => {
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-critical-unknown-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-critical-unknown-annotation.js
index b7b184ddd0..32d1c29a59 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-critical-unknown-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-critical-unknown-annotation.js
@@ -13,7 +13,7 @@ const invalidStrings = [
   "1970-01-01T00:00[UTC][u-ca=iso8601][!foo=bar]",
   "1970-01-01T00:00[foo=bar][!_foo-bar0=Dont-Ignore-This-99999999999]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach((arg) => {
   assert.throws(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-date-with-utc-offset.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-date-with-utc-offset.js
index 6ceb051eb3..f1dfa246d0 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-date-with-utc-offset.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-date-with-utc-offset.js
@@ -8,7 +8,7 @@ features: [Temporal]
 includes: [temporalHelpers.js]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const validStrings = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-multiple-calendar.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-multiple-calendar.js
index 4e6737e183..4154f1e92d 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-multiple-calendar.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-multiple-calendar.js
@@ -14,7 +14,7 @@ const invalidStrings = [
   "1970-01-01T00:00[UTC][!u-ca=iso8601][u-ca=iso8601]",
   "1970-01-01T00:00[UTC][u-ca=iso8601][foo=bar][!u-ca=iso8601]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach((arg) => {
   assert.throws(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-multiple-time-zone.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-multiple-time-zone.js
index c5c328d3c6..c98ac91db8 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-multiple-time-zone.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-multiple-time-zone.js
@@ -14,7 +14,7 @@ const invalidStrings = [
   "1970-01-01T00:00[UTC][u-ca=iso8601][UTC]",
   "1970-01-01T00:00[UTC][foo=bar][UTC]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach((arg) => {
   assert.throws(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-time-separators.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-time-separators.js
index 1e5915d4ec..81560e5ae6 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-time-separators.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-time-separators.js
@@ -14,7 +14,7 @@ const tests = [
   ["1970-01-01 00:00+00:00[UTC]", "space between date and time"],
 ];
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 tests.forEach(([arg, description]) => {
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-time-zone-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-time-zone-annotation.js
index cdf5de9ff5..ac780489ca 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-time-zone-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-time-zone-annotation.js
@@ -23,7 +23,7 @@ const tests = [
   ["1970-01-01T00:00+00:00[!+00:00]", "numeric, with offset and !"],
 ];
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 tests.forEach(([arg, description]) => {
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-unknown-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-unknown-annotation.js
index 8e3b643be9..b42a0960d9 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-unknown-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-unknown-annotation.js
@@ -15,7 +15,7 @@ const tests = [
   ["1970-01-01T00:00[UTC][foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
 ];
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 tests.forEach(([arg, description]) => {
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-wrong-type.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-wrong-type.js
index 65793e8dec..253d4a1a11 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-wrong-type.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/balance-negative-time-units.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/balance-negative-time-units.js
index 801b00cd19..bface19af8 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/balance-negative-time-units.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/balance-negative-time-units.js
@@ -30,7 +30,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const datetime = new Temporal.ZonedDateTime(830998861_001_001_001n, timeZone);
 const options = { largestUnit: "days" };
 
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/branding.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/branding.js
index 5695e13f2e..4c1efdf444 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/branding.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/branding.js
@@ -11,7 +11,7 @@ const since = Temporal.ZonedDateTime.prototype.since;
 
 assert.sameValue(typeof since, "function");
 
-const args = [new Temporal.ZonedDateTime(123456n, new Temporal.TimeZone("UTC"))];
+const args = [new Temporal.ZonedDateTime(123456n, "UTC")];
 
 assert.throws(TypeError, () => since.apply(undefined, args), "undefined");
 assert.throws(TypeError, () => since.apply(null, args), "null");
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/leap-second.js
index e3611500bb..cc1e4ec3b7 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/leap-second.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/leap-second.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(1_483_228_799_000_000_000n, timeZone);
 
 let arg = "2016-12-31T23:59:60+00:00[UTC]";
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/year-zero.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/year-zero.js
index a33e732fba..0d246a0732 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/year-zero.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/year-zero.js
@@ -12,7 +12,7 @@ const invalidStrings = [
   "-0000000-01-01T00:02+00:00[UTC]",
   "-0000000-01-01T00:02:00.000000000+00:00[UTC]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach((arg) => {
   assert.throws(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/zoneddatetime-string-multiple-offsets.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/zoneddatetime-string-multiple-offsets.js
index d973fd768c..54388a33a6 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/zoneddatetime-string-multiple-offsets.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/zoneddatetime-string-multiple-offsets.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("+01:35");
+const timeZone = "+01:35";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 let str = "1970-01-01T01:35:30+01:35:00.000000000[+01:35]";
 
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/zoneddatetime-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/zoneddatetime-string.js
index 6d641e291a..6886504ad9 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/zoneddatetime-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/zoneddatetime-string.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 let str = "1970-01-01T00:00";
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/toJSON/offset.js b/test/built-ins/Temporal/ZonedDateTime/prototype/toJSON/offset.js
index e3246b9946..36d1f8a47b 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/toJSON/offset.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/toJSON/offset.js
@@ -8,8 +8,7 @@ features: [BigInt, Temporal]
 ---*/
 
 function test(timeZoneIdentifier, expected, description) {
-  const timeZone = new Temporal.TimeZone(timeZoneIdentifier);
-  const datetime = new Temporal.ZonedDateTime(0n, timeZone);
+  const datetime = new Temporal.ZonedDateTime(0n, timeZoneIdentifier);
   assert.sameValue(datetime.toJSON(), expected, description);
 }
 
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/toJSON/year-format.js b/test/built-ins/Temporal/ZonedDateTime/prototype/toJSON/year-format.js
index d532f99c4a..64bdf8d41d 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/toJSON/year-format.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/toJSON/year-format.js
@@ -13,43 +13,41 @@ function epochNsInYear(year) {
   return (year - 1970n) * avgNsPerYear + (avgNsPerYear / 2n);
 }
 
-const utc = new Temporal.TimeZone("UTC");
-
-let instance = new Temporal.ZonedDateTime(epochNsInYear(-100000n), utc);
+let instance = new Temporal.ZonedDateTime(epochNsInYear(-100000n), "UTC");
 assert.sameValue(instance.toJSON(), "-100000-07-01T21:30:36+00:00[UTC]", "large negative year formatted as 6-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(-10000n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(-10000n), "UTC");
 assert.sameValue(instance.toJSON(), "-010000-07-01T21:30:36+00:00[UTC]", "smallest 5-digit negative year formatted as 6-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(-9999n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(-9999n), "UTC");
 assert.sameValue(instance.toJSON(), "-009999-07-02T03:19:48+00:00[UTC]", "largest 4-digit negative year formatted as 6-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(-1000n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(-1000n), "UTC");
 assert.sameValue(instance.toJSON(), "-001000-07-02T09:30:36+00:00[UTC]", "smallest 4-digit negative year formatted as 6-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(-999n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(-999n), "UTC");
 assert.sameValue(instance.toJSON(), "-000999-07-02T15:19:48+00:00[UTC]", "largest 3-digit negative year formatted as 6-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(-1n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(-1n), "UTC");
 assert.sameValue(instance.toJSON(), "-000001-07-02T15:41:24+00:00[UTC]", "year -1 formatted as 6-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(0n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(0n), "UTC");
 assert.sameValue(instance.toJSON(), "0000-07-01T21:30:36+00:00[UTC]", "year 0 formatted as 4-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(1n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(1n), "UTC");
 assert.sameValue(instance.toJSON(), "0001-07-02T03:19:48+00:00[UTC]", "year 1 formatted as 4-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(999n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(999n), "UTC");
 assert.sameValue(instance.toJSON(), "0999-07-02T03:41:24+00:00[UTC]", "largest 3-digit positive year formatted as 4-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(1000n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(1000n), "UTC");
 assert.sameValue(instance.toJSON(), "1000-07-02T09:30:36+00:00[UTC]", "smallest 4-digit positive year formatted as 4-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(9999n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(9999n), "UTC");
 assert.sameValue(instance.toJSON(), "9999-07-02T15:41:24+00:00[UTC]", "largest 4-digit positive year formatted as 4-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(10000n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(10000n), "UTC");
 assert.sameValue(instance.toJSON(), "+010000-07-01T21:30:36+00:00[UTC]", "smallest 5-digit positive year formatted as 6-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(100000n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(100000n), "UTC");
 assert.sameValue(instance.toJSON(), "+100000-07-01T21:30:36+00:00[UTC]", "large positive year formatted as 6-digit");
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/toString/offset.js b/test/built-ins/Temporal/ZonedDateTime/prototype/toString/offset.js
index 5ff25b6c71..69905f17c6 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/toString/offset.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/toString/offset.js
@@ -8,8 +8,7 @@ features: [BigInt, Temporal]
 ---*/
 
 function test(timeZoneIdentifier, expected, description) {
-  const timeZone = new Temporal.TimeZone(timeZoneIdentifier);
-  const datetime = new Temporal.ZonedDateTime(0n, timeZone);
+  const datetime = new Temporal.ZonedDateTime(0n, timeZoneIdentifier);
   assert.sameValue(datetime.toString(), expected, description);
 }
 
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/toString/year-format.js b/test/built-ins/Temporal/ZonedDateTime/prototype/toString/year-format.js
index 1532bf1fec..7b4e51ac5a 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/toString/year-format.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/toString/year-format.js
@@ -13,43 +13,41 @@ function epochNsInYear(year) {
   return (year - 1970n) * avgNsPerYear + (avgNsPerYear / 2n);
 }
 
-const utc = new Temporal.TimeZone("UTC");
-
-let instance = new Temporal.ZonedDateTime(epochNsInYear(-100000n), utc);
+let instance = new Temporal.ZonedDateTime(epochNsInYear(-100000n), "UTC");
 assert.sameValue(instance.toString(), "-100000-07-01T21:30:36+00:00[UTC]", "large negative year formatted as 6-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(-10000n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(-10000n), "UTC");
 assert.sameValue(instance.toString(), "-010000-07-01T21:30:36+00:00[UTC]", "smallest 5-digit negative year formatted as 6-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(-9999n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(-9999n), "UTC");
 assert.sameValue(instance.toString(), "-009999-07-02T03:19:48+00:00[UTC]", "largest 4-digit negative year formatted as 6-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(-1000n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(-1000n), "UTC");
 assert.sameValue(instance.toString(), "-001000-07-02T09:30:36+00:00[UTC]", "smallest 4-digit negative year formatted as 6-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(-999n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(-999n), "UTC");
 assert.sameValue(instance.toString(), "-000999-07-02T15:19:48+00:00[UTC]", "largest 3-digit negative year formatted as 6-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(-1n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(-1n), "UTC");
 assert.sameValue(instance.toString(), "-000001-07-02T15:41:24+00:00[UTC]", "year -1 formatted as 6-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(0n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(0n), "UTC");
 assert.sameValue(instance.toString(), "0000-07-01T21:30:36+00:00[UTC]", "year 0 formatted as 4-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(1n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(1n), "UTC");
 assert.sameValue(instance.toString(), "0001-07-02T03:19:48+00:00[UTC]", "year 1 formatted as 4-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(999n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(999n), "UTC");
 assert.sameValue(instance.toString(), "0999-07-02T03:41:24+00:00[UTC]", "largest 3-digit positive year formatted as 4-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(1000n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(1000n), "UTC");
 assert.sameValue(instance.toString(), "1000-07-02T09:30:36+00:00[UTC]", "smallest 4-digit positive year formatted as 4-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(9999n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(9999n), "UTC");
 assert.sameValue(instance.toString(), "9999-07-02T15:41:24+00:00[UTC]", "largest 4-digit positive year formatted as 4-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(10000n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(10000n), "UTC");
 assert.sameValue(instance.toString(), "+010000-07-01T21:30:36+00:00[UTC]", "smallest 5-digit positive year formatted as 6-digit");
 
-instance = new Temporal.ZonedDateTime(epochNsInYear(100000n), utc);
+instance = new Temporal.ZonedDateTime(epochNsInYear(100000n), "UTC");
 assert.sameValue(instance.toString(), "+100000-07-01T21:30:36+00:00[UTC]", "large positive year formatted as 6-digit");
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-case-insensitive.js
index 1dd8006d86..0ca4690f92 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-case-insensitive.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar: "IsO8601" };
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-iso-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-iso-string.js
index b3dac55ef3..4b16970970 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-iso-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-iso-string.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 for (const calendar of [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-leap-second.js
index 3d98103d93..2330baf215 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-leap-second.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-leap-second.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const calendar = "2016-12-31T23:59:60+00:00[UTC]";
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-number.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-number.js
index c3e14bef3f..c3a0450817 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-number.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-number.js
@@ -7,7 +7,7 @@ description: A number as calendar in a property bag is not accepted
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const numbers = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-string.js
index 792f99d3e2..2236448ccf 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-string.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const calendar = "iso8601";
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-wrong-type.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-wrong-type.js
index fea32897da..7e61e42a92 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-wrong-type.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-wrong-type.js
@@ -5,11 +5,11 @@
 esid: sec-temporal.zoneddatetime.prototype.until
 description: >
   Appropriate error thrown when a calendar property from a property bag cannot
-  be converted to a calendar object or string
+  be converted to a calendar ID
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-year-zero.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-year-zero.js
index be524e3ecb..34a8809268 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-year-zero.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-year-zero.js
@@ -14,7 +14,7 @@ const invalidStrings = [
   "-000000-10-31T17:45+01:00",
   "-000000-10-31T17:45+00:00[UTC]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach((str) => {
   const arg = { year: 1976, month: 11, day: 18, calendar: str };
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-invalid-offset-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-invalid-offset-string.js
index 65c1091f9b..09a001384a 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-invalid-offset-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-invalid-offset-string.js
@@ -7,7 +7,7 @@ description: Property bag with offset property is rejected if offset is in the w
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const badOffsets = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-offset-not-agreeing-with-timezone.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-offset-not-agreeing-with-timezone.js
index 1895808b8c..692451011d 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-offset-not-agreeing-with-timezone.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-offset-not-agreeing-with-timezone.js
@@ -7,7 +7,7 @@ description: Property bag with offset property is rejected if offset does not ag
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("+01:00");
+const timeZone = "+01:00";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const properties = { year: 2021, month: 10, day: 28, offset: "-07:00", timeZone };
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-timezone-string-year-zero.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-timezone-string-year-zero.js
index 3e01e23583..90604c9d5b 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-timezone-string-year-zero.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-timezone-string-year-zero.js
@@ -11,7 +11,7 @@ const invalidStrings = [
   "-000000-10-31T17:45Z",
   "-000000-10-31T17:45+00:00[UTC]",
 ];
-const instance = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("UTC"));
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 invalidStrings.forEach((timeZone) => {
   assert.throws(
     RangeError,
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-timezone-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-timezone-string.js
index 3e6f906f49..2e49c2d59e 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-timezone-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-timezone-string.js
@@ -25,10 +25,10 @@ Object.defineProperty(Temporal.TimeZone.prototype, "getOffsetNanosecondsFor", {
   },
 });
 
-const instance1 = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("UTC"));
+const instance1 = new Temporal.ZonedDateTime(0n, "UTC");
 assert(instance1.until({ year: 1970, month: 1, day: 1, timeZone: "UTC" }).blank, "Time zone created from string 'UTC'");
 
-const instance2 = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("-01:30"));
+const instance2 = new Temporal.ZonedDateTime(0n, "-01:30");
 assert(instance2.until({ year: 1969, month: 12, day: 31, hour: 22, minute: 30, timeZone: "-01:30" }).blank, "Time zone created from string '-01:30'");
 
 Object.defineProperty(Temporal.TimeZone.prototype, "getPossibleInstantsFor", getPossibleInstantsForOriginal);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-timezone-wrong-type.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-timezone-wrong-type.js
index 479d405086..31db013f80 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-timezone-wrong-type.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-timezone-wrong-type.js
@@ -5,11 +5,11 @@
 esid: sec-temporal.zoneddatetime.prototype.until
 description: >
   Appropriate error thrown when argument cannot be converted to a valid string
-  or object for TimeZone
+  for time zone
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const instance = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("UTC"));
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 
 const primitiveTests = [
   [null, "null"],
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-calendar-annotation-invalid-key.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-calendar-annotation-invalid-key.js
index 4375637118..4a71e7829a 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-calendar-annotation-invalid-key.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-calendar-annotation-invalid-key.js
@@ -12,7 +12,7 @@ const invalidStrings = [
   ["1970-01-01T00:00[UTC][u-CA=iso8601]", "invalid partially-capitalized key"],
   ["1970-01-01T00:00[UTC][FOO=bar]", "invalid capitalized unrecognized key"],
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach(([arg, descr]) => {
   assert.throws(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-calendar-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-calendar-annotation.js
index 832a57b7c5..8f2fda4fea 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-calendar-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-calendar-annotation.js
@@ -14,7 +14,7 @@ const tests = [
   ["1970-01-01T00:00[UTC][u-ca=iso8601][u-ca=discord]", "second annotation ignored"],
 ];
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 tests.forEach(([arg, description]) => {
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-critical-unknown-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-critical-unknown-annotation.js
index a29b7bc4c8..4b1fdb5b9c 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-critical-unknown-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-critical-unknown-annotation.js
@@ -13,7 +13,7 @@ const invalidStrings = [
   "1970-01-01T00:00[UTC][u-ca=iso8601][!foo=bar]",
   "1970-01-01T00:00[foo=bar][!_foo-bar0=Dont-Ignore-This-99999999999]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach((arg) => {
   assert.throws(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-date-with-utc-offset.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-date-with-utc-offset.js
index 5e36bdaf70..2c9709e78f 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-date-with-utc-offset.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-date-with-utc-offset.js
@@ -8,7 +8,7 @@ features: [Temporal]
 includes: [temporalHelpers.js]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const validStrings = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-multiple-calendar.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-multiple-calendar.js
index 1d028c5482..e79b2980c1 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-multiple-calendar.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-multiple-calendar.js
@@ -14,7 +14,7 @@ const invalidStrings = [
   "1970-01-01T00:00[UTC][!u-ca=iso8601][u-ca=iso8601]",
   "1970-01-01T00:00[UTC][u-ca=iso8601][foo=bar][!u-ca=iso8601]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach((arg) => {
   assert.throws(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-multiple-time-zone.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-multiple-time-zone.js
index 5a9d0c16bc..b9810322c3 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-multiple-time-zone.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-multiple-time-zone.js
@@ -14,7 +14,7 @@ const invalidStrings = [
   "1970-01-01T00:00[UTC][u-ca=iso8601][UTC]",
   "1970-01-01T00:00[UTC][foo=bar][UTC]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach((arg) => {
   assert.throws(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-time-separators.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-time-separators.js
index 10cf351352..9e4cd13d99 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-time-separators.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-time-separators.js
@@ -14,7 +14,7 @@ const tests = [
   ["1970-01-01 00:00+00:00[UTC]", "space between date and time"],
 ];
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 tests.forEach(([arg, description]) => {
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-time-zone-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-time-zone-annotation.js
index 37ed65f309..8c2a81a2cf 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-time-zone-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-time-zone-annotation.js
@@ -23,7 +23,7 @@ const tests = [
   ["1970-01-01T00:00+00:00[!+00:00]", "numeric, with offset and !"],
 ];
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 tests.forEach(([arg, description]) => {
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-unknown-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-unknown-annotation.js
index 471ef89415..9b3e67b272 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-unknown-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-unknown-annotation.js
@@ -15,7 +15,7 @@ const tests = [
   ["1970-01-01T00:00[UTC][foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
 ];
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 tests.forEach(([arg, description]) => {
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-wrong-type.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-wrong-type.js
index 528825459d..d534310635 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-wrong-type.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-wrong-type.js
@@ -9,7 +9,7 @@ description: >
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const primitiveTests = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/balance-negative-time-units.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/balance-negative-time-units.js
index 2005406753..376d45f575 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/balance-negative-time-units.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/balance-negative-time-units.js
@@ -30,25 +30,24 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
-const datetime = new Temporal.ZonedDateTime(830998861_001_001_001n, timeZone);
+const datetime = new Temporal.ZonedDateTime(830998861_001_001_001n, "UTC");
 const options = { largestUnit: "days" };
 
-const result1 = new Temporal.ZonedDateTime(830995200_000_000_002n, timeZone).until(datetime, options);
+const result1 = new Temporal.ZonedDateTime(830995200_000_000_002n, "UTC").until(datetime, options);
 TemporalHelpers.assertDuration(result1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 999, "nanoseconds balance");
 
-const result2 = new Temporal.ZonedDateTime(830995200_000_002_000n, timeZone).until(datetime, options);
+const result2 = new Temporal.ZonedDateTime(830995200_000_002_000n, "UTC").until(datetime, options);
 TemporalHelpers.assertDuration(result2, 0, 0, 0, 0, 1, 1, 1, 0, 999, 1, "microseconds balance");
 
-const result3 = new Temporal.ZonedDateTime(830995200_002_000_000n, timeZone).until(datetime, options);
+const result3 = new Temporal.ZonedDateTime(830995200_002_000_000n, "UTC").until(datetime, options);
 TemporalHelpers.assertDuration(result3, 0, 0, 0, 0, 1, 1, 0, 999, 1, 1, "milliseconds balance");
 
-const result4 = new Temporal.ZonedDateTime(830995202_000_000_000n, timeZone).until(datetime, options);
+const result4 = new Temporal.ZonedDateTime(830995202_000_000_000n, "UTC").until(datetime, options);
 TemporalHelpers.assertDuration(result4, 0, 0, 0, 0, 1, 0, 59, 1, 1, 1, "seconds balance");
 
-const result5 = new Temporal.ZonedDateTime(830995320_000_000_000n, timeZone).until(datetime, options);
+const result5 = new Temporal.ZonedDateTime(830995320_000_000_000n, "UTC").until(datetime, options);
 TemporalHelpers.assertDuration(result5, 0, 0, 0, 0, 0, 59, 1, 1, 1, 1, "minutes balance");
 
 // This one is different because hours are later balanced again in BalanceDuration
-const result6 = new Temporal.ZonedDateTime(831002400_000_000_000n, timeZone).until(datetime, options);
+const result6 = new Temporal.ZonedDateTime(831002400_000_000_000n, "UTC").until(datetime, options);
 TemporalHelpers.assertDuration(result6, 0, 0, 0, 0, 0, -58, -58, -998, -998, -999, "hours balance");
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/branding.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/branding.js
index a84b29e76b..e5cc9d8077 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/branding.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/branding.js
@@ -11,7 +11,7 @@ const until = Temporal.ZonedDateTime.prototype.until;
 
 assert.sameValue(typeof until, "function");
 
-const args = [new Temporal.ZonedDateTime(123456n, new Temporal.TimeZone("UTC"))];
+const args = [new Temporal.ZonedDateTime(123456n, "UTC")];
 
 assert.throws(TypeError, () => until.apply(undefined, args), "undefined");
 assert.throws(TypeError, () => until.apply(null, args), "null");
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/leap-second.js
index ffa342eff0..4517b535df 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/leap-second.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/leap-second.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(1_483_228_799_000_000_000n, timeZone);
 
 let arg = "2016-12-31T23:59:60+00:00[UTC]";
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/year-zero.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/year-zero.js
index fb6e140e22..5fcece628f 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/year-zero.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/year-zero.js
@@ -12,7 +12,7 @@ const invalidStrings = [
   "-0000000-01-01T00:02+00:00[UTC]",
   "-0000000-01-01T00:02:00.000000000+00:00[UTC]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach((arg) => {
   assert.throws(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/zoneddatetime-string-multiple-offsets.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/zoneddatetime-string-multiple-offsets.js
index 6330d8710b..988ade63ce 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/zoneddatetime-string-multiple-offsets.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/zoneddatetime-string-multiple-offsets.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("+01:35");
+const timeZone = "+01:35";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 let str = "1970-01-01T01:35:30+01:35:00.000000000[+01:35]";
 
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/zoneddatetime-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/zoneddatetime-string.js
index 1cf959aa4e..25e392b676 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/zoneddatetime-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/zoneddatetime-string.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 let str = "1970-01-01T00:00";
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/with/offset-property-invalid-string.js b/test/built-ins/Temporal/ZonedDateTime/prototype/with/offset-property-invalid-string.js
index 432a00c595..8d9bdb0f3b 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/with/offset-property-invalid-string.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/with/offset-property-invalid-string.js
@@ -7,8 +7,7 @@ description: Property bag with offset property is rejected if offset is in the w
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
-const instance = new Temporal.ZonedDateTime(0n, timeZone);
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 
 const offsetOptions = ['use', 'prefer', 'ignore', 'reject'];
 
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/with/offset-undefined.js b/test/built-ins/Temporal/ZonedDateTime/prototype/with/offset-undefined.js
index f1b6b8423e..0d96c9aacc 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/with/offset-undefined.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/with/offset-undefined.js
@@ -14,9 +14,7 @@ info: |
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("-03:30");
-
-const datetime = new Temporal.ZonedDateTime(1572757201_000_000_000n, timeZone);
+const datetime = new Temporal.ZonedDateTime(1572757201_000_000_000n, "-03:30");
 const explicit = datetime.with({ minute: 31 }, { offset: undefined });
 assert.sameValue(explicit.epochNanoseconds, 1572757261_000_000_000n, "default offset is prefer");
 const implicit = datetime.with({ minute: 31 }, {});
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withCalendar/branding.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withCalendar/branding.js
index 1533200c97..b68d98bef9 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withCalendar/branding.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withCalendar/branding.js
@@ -11,7 +11,7 @@ const withCalendar = Temporal.ZonedDateTime.prototype.withCalendar;
 
 assert.sameValue(typeof withCalendar, "function");
 
-const args = [new Temporal.Calendar("iso8601")];
+const args = ["iso8601"];
 
 assert.throws(TypeError, () => withCalendar.apply(undefined, args), "undefined");
 assert.throws(TypeError, () => withCalendar.apply(null, args), "null");
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-calendar-annotation-invalid-key.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-calendar-annotation-invalid-key.js
index 32b59887c0..1ff0de2d06 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-calendar-annotation-invalid-key.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-calendar-annotation-invalid-key.js
@@ -18,7 +18,7 @@ const invalidStrings = [
   ["T00:00[FOO=bar]", "invalid capitalized unrecognized key, time designator"],
   ["1970-01-01T00:00[FOO=bar]", "invalid capitalized unrecognized key"],
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach(([arg, descr]) => {
   assert.throws(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-calendar-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-calendar-annotation.js
index fc696e7975..073e2d7ad1 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-calendar-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-calendar-annotation.js
@@ -26,7 +26,7 @@ const tests = [
   ["1970-01-01T12:34:56.987654321[u-ca=iso8601][u-ca=discord]", "second annotation ignored"],
 ];
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 tests.forEach(([arg, description]) => {
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-critical-unknown-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-critical-unknown-annotation.js
index 3ae28dfd0c..cde62d40c9 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-critical-unknown-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-critical-unknown-annotation.js
@@ -16,7 +16,7 @@ const invalidStrings = [
   "1970-01-01T00:00[UTC][!foo=bar][u-ca=iso8601]",
   "1970-01-01T00:00[foo=bar][!_foo-bar0=Dont-Ignore-This-99999999999]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach((arg) => {
   assert.throws(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-date-with-utc-offset.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-date-with-utc-offset.js
index d50b266807..07c1e8ebc3 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-date-with-utc-offset.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-date-with-utc-offset.js
@@ -7,7 +7,7 @@ description: UTC offset not valid with format that does not include a time
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 const validStrings = [
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-multiple-calendar.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-multiple-calendar.js
index 7b83150ee5..ced0b5925b 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-multiple-calendar.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-multiple-calendar.js
@@ -19,7 +19,7 @@ const invalidStrings = [
   "1970-01-01T00:00[UTC][u-ca=iso8601][!u-ca=iso8601]",
   "1970-01-01T00:00[u-ca=iso8601][foo=bar][!u-ca=iso8601]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach((arg) => {
   assert.throws(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-multiple-time-zone.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-multiple-time-zone.js
index 56a8c76342..5398e4c54e 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-multiple-time-zone.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-multiple-time-zone.js
@@ -16,7 +16,7 @@ const invalidStrings = [
   "1970-01-01T00:00[UTC][u-ca=iso8601][UTC]",
   "1970-01-01T00:00[UTC][foo=bar][UTC]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach((arg) => {
   assert.throws(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-time-separators.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-time-separators.js
index cb37471609..5e492936ae 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-time-separators.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-time-separators.js
@@ -15,7 +15,7 @@ const tests = [
   ["t12:34:56.987654321", "time-only lowercase T"],
 ];
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 tests.forEach(([arg, description]) => {
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-time-zone-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-time-zone-annotation.js
index 08abc6d058..01b10c3f20 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-time-zone-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-time-zone-annotation.js
@@ -34,7 +34,7 @@ const tests = [
   ["1970-01-01T12:34:56.987654321+00:00[!-08:00]", "numeric, with date, offset, and !"],
 ];
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 tests.forEach(([arg, description]) => {
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-unknown-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-unknown-annotation.js
index f5e4e9395c..7eb4ef2251 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-unknown-annotation.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-unknown-annotation.js
@@ -23,7 +23,7 @@ const tests = [
   ["1970-01-01T12:34:56.987654321[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
 ];
 
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 tests.forEach(([arg, description]) => {
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-zoneddatetime-balance-negative-time-units.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-zoneddatetime-balance-negative-time-units.js
index 8ece6fc605..7101425811 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-zoneddatetime-balance-negative-time-units.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-zoneddatetime-balance-negative-time-units.js
@@ -38,8 +38,7 @@ features: [Temporal]
 const tz = TemporalHelpers.specificOffsetTimeZone(-2);
 const datetime = new Temporal.ZonedDateTime(3661_001_001_001n, tz);
 
-const otherTimeZone = new Temporal.TimeZone("UTC"); // should not be used to convert datetime -> PlainTime
-const zdt = new Temporal.ZonedDateTime(86400_000_000_000n, otherTimeZone);
+const zdt = new Temporal.ZonedDateTime(86400_000_000_000n, "UTC"); // UTC should not be used to convert datetime -> PlainTime
 const newzdt = zdt.withPlainTime(datetime);
 
 assert.sameValue(newzdt.microsecond, 0);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/year-zero.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/year-zero.js
index f5fa8e920e..baf1f69258 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/year-zero.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/year-zero.js
@@ -12,7 +12,7 @@ const invalidStrings = [
   "-000000-12-07T03:24:30+01:00",
   "-000000-12-07T03:24:30+00:00[UTC]",
 ];
-const timeZone = new Temporal.TimeZone("UTC");
+const timeZone = "UTC";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 invalidStrings.forEach((arg) => {
   assert.throws(
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/branding.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/branding.js
index feecfe91b3..f5f3f4a66c 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/branding.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/branding.js
@@ -11,7 +11,7 @@ const withTimeZone = Temporal.ZonedDateTime.prototype.withTimeZone;
 
 assert.sameValue(typeof withTimeZone, "function");
 
-const args = [new Temporal.TimeZone("UTC")];
+const args = ["UTC"];
 
 assert.throws(TypeError, () => withTimeZone.apply(undefined, args), "undefined");
 assert.throws(TypeError, () => withTimeZone.apply(null, args), "null");
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/timezone-string-year-zero.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/timezone-string-year-zero.js
index 727174f1b2..63850e353f 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/timezone-string-year-zero.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/timezone-string-year-zero.js
@@ -11,7 +11,7 @@ const invalidStrings = [
   "-000000-10-31T17:45Z",
   "-000000-10-31T17:45+00:00[UTC]",
 ];
-const instance = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("UTC"));
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 invalidStrings.forEach((timeZone) => {
   assert.throws(
     RangeError,
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/timezone-wrong-type.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/timezone-wrong-type.js
index 2f185583f5..ef042f4e23 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/timezone-wrong-type.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/timezone-wrong-type.js
@@ -5,11 +5,11 @@
 esid: sec-temporal.zoneddatetime.prototype.withtimezone
 description: >
   Appropriate error thrown when argument cannot be converted to a valid string
-  or object for TimeZone
+  for time zone
 features: [BigInt, Symbol, Temporal]
 ---*/
 
-const instance = new Temporal.ZonedDateTime(0n, new Temporal.TimeZone("UTC"));
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
 
 const primitiveTests = [
   [null, "null"],
diff --git a/test/intl402/Temporal/Duration/compare/relativeto-sub-minute-offset.js b/test/intl402/Temporal/Duration/compare/relativeto-sub-minute-offset.js
index 67e842da79..b7fc245bda 100644
--- a/test/intl402/Temporal/Duration/compare/relativeto-sub-minute-offset.js
+++ b/test/intl402/Temporal/Duration/compare/relativeto-sub-minute-offset.js
@@ -23,6 +23,5 @@ relativeTo = "1970-01-01T00:00:00-00:44:30[Africa/Monrovia]";
 result = action(relativeTo);
 assert.sameValue(result, 0, "unrounded HH:MM:SS is accepted in string offset");
 
-const timeZone = Temporal.TimeZone.from("Africa/Monrovia");
-relativeTo = { year: 1970, month: 1, day: 1, offset: "+00:45", timeZone };
+relativeTo = { year: 1970, month: 1, day: 1, offset: "+00:45", timeZone: "Africa/Monrovia" };
 assert.throws(RangeError, () => action(relativeTo), "rounded HH:MM not accepted as offset in property bag");
diff --git a/test/intl402/Temporal/Duration/prototype/round/relativeto-sub-minute-offset.js b/test/intl402/Temporal/Duration/prototype/round/relativeto-sub-minute-offset.js
index aa0c86ce82..5ffe35e2a3 100644
--- a/test/intl402/Temporal/Duration/prototype/round/relativeto-sub-minute-offset.js
+++ b/test/intl402/Temporal/Duration/prototype/round/relativeto-sub-minute-offset.js
@@ -34,6 +34,5 @@ TemporalHelpers.assertDateDuration(result, 1, 0, 0, 1, "unrounded HH:MM:SS is ac
 relativeTo = "1970-01-01T00:00+00:44:30.123456789[+00:45]";
 assert.throws(RangeError, () => action(relativeTo), "rounding is not accepted between ISO offset and time zone");
 
-const timeZone = Temporal.TimeZone.from("Africa/Monrovia");
-relativeTo = { year: 1970, month: 1, day: 1, offset: "+00:45", timeZone };
+relativeTo = { year: 1970, month: 1, day: 1, offset: "+00:45", timeZone: "Africa/Monrovia" };
 assert.throws(RangeError, () => action(relativeTo), "rounded HH:MM not accepted as offset in property bag");
diff --git a/test/intl402/Temporal/Duration/prototype/total/relativeto-sub-minute-offset.js b/test/intl402/Temporal/Duration/prototype/total/relativeto-sub-minute-offset.js
index a3e664ca31..e878ce90c5 100644
--- a/test/intl402/Temporal/Duration/prototype/total/relativeto-sub-minute-offset.js
+++ b/test/intl402/Temporal/Duration/prototype/total/relativeto-sub-minute-offset.js
@@ -33,6 +33,5 @@ assert.sameValue(result, 366, "unrounded HH:MM:SS is accepted in string offset")
 relativeTo = "1970-01-01T00:00+00:44:30.123456789[+00:45]";
 assert.throws(RangeError, () => action(relativeTo), "rounding is not accepted between ISO offset and time zone");
 
-const timeZone = Temporal.TimeZone.from("Africa/Monrovia");
-relativeTo = { year: 1970, month: 1, day: 1, offset: "+00:45", timeZone };
+relativeTo = { year: 1970, month: 1, day: 1, offset: "+00:45", timeZone: "Africa/Monrovia" };
 assert.throws(RangeError, () => action(relativeTo), "rounded HH:MM not accepted as offset in property bag");
diff --git a/test/intl402/Temporal/Instant/prototype/toString/timezone-offset.js b/test/intl402/Temporal/Instant/prototype/toString/timezone-offset.js
index 7016baa59d..167a21ad16 100644
--- a/test/intl402/Temporal/Instant/prototype/toString/timezone-offset.js
+++ b/test/intl402/Temporal/Instant/prototype/toString/timezone-offset.js
@@ -9,8 +9,7 @@ features: [BigInt, Temporal]
 
 const instant = new Temporal.Instant(0n);
 
-function test(timeZoneIdentifier, expected, description) {
-  const timeZone = new Temporal.TimeZone(timeZoneIdentifier);
+function test(timeZone, expected, description) {
   assert.sameValue(instant.toString({ timeZone }), expected, description);
 }
 
diff --git a/test/intl402/Temporal/PlainDate/prototype/weekOfYear/gregory-iso-weekofyear.js b/test/intl402/Temporal/PlainDate/prototype/weekOfYear/gregory-iso-weekofyear.js
index 4d02382335..65d04659e4 100644
--- a/test/intl402/Temporal/PlainDate/prototype/weekOfYear/gregory-iso-weekofyear.js
+++ b/test/intl402/Temporal/PlainDate/prototype/weekOfYear/gregory-iso-weekofyear.js
@@ -16,12 +16,12 @@ features: [Temporal]
 
 // 
 
-let calendar = new Temporal.Calendar("gregory");
+let calendar = "gregory";
 const date = new Temporal.PlainDate(2021, 1, 1, calendar);
 
 assert.sameValue(date.weekOfYear, 1);
 
-calendar = new Temporal.Calendar("iso8601");
+calendar = "iso8601";
 const isodate = new Temporal.PlainDate(2021, 1, 1, calendar);
 
 assert.sameValue(isodate.weekOfYear, 53);
diff --git a/test/intl402/Temporal/PlainDate/prototype/weekOfYear/non-iso-week-of-year.js b/test/intl402/Temporal/PlainDate/prototype/weekOfYear/non-iso-week-of-year.js
index 86c46b497d..88e9e59314 100644
--- a/test/intl402/Temporal/PlainDate/prototype/weekOfYear/non-iso-week-of-year.js
+++ b/test/intl402/Temporal/PlainDate/prototype/weekOfYear/non-iso-week-of-year.js
@@ -11,12 +11,12 @@ features: [Temporal]
 
 // Gregorian calendar has a well defined week-numbering system.
 
-let calendar = new Temporal.Calendar("gregory");
+let calendar = "gregory";
 const date = new Temporal.PlainDate(2024, 1, 1, calendar);
 
 assert.sameValue(date.weekOfYear, 1);
 
-calendar = new Temporal.Calendar("hebrew");
+calendar = "hebrew";
 const nonisodate = new Temporal.PlainDate(2024, 1, 1, calendar);
 
 assert.sameValue(nonisodate.weekOfYear, undefined);
diff --git a/test/intl402/Temporal/PlainDate/prototype/yearOfWeek/gregory-iso-weekofyear.js b/test/intl402/Temporal/PlainDate/prototype/yearOfWeek/gregory-iso-weekofyear.js
index 70252942e9..8de9cc6f34 100644
--- a/test/intl402/Temporal/PlainDate/prototype/yearOfWeek/gregory-iso-weekofyear.js
+++ b/test/intl402/Temporal/PlainDate/prototype/yearOfWeek/gregory-iso-weekofyear.js
@@ -16,12 +16,12 @@ features: [Temporal]
 
 // 
 
-let calendar = new Temporal.Calendar("gregory");
+let calendar = "gregory";
 const date = new Temporal.PlainDate(2021, 1, 1, calendar);
 
 assert.sameValue(date.yearOfWeek, 2021);
 
-calendar = new Temporal.Calendar("iso8601");
+calendar = "iso8601";
 const isodate = new Temporal.PlainDate(2021, 1, 1, calendar);
 
 assert.sameValue(isodate.yearOfWeek, 2020);
diff --git a/test/intl402/Temporal/PlainDate/prototype/yearOfWeek/non-iso-week-of-year.js b/test/intl402/Temporal/PlainDate/prototype/yearOfWeek/non-iso-week-of-year.js
index e378c0884c..5d0190e259 100644
--- a/test/intl402/Temporal/PlainDate/prototype/yearOfWeek/non-iso-week-of-year.js
+++ b/test/intl402/Temporal/PlainDate/prototype/yearOfWeek/non-iso-week-of-year.js
@@ -11,12 +11,12 @@ features: [Temporal]
 
 // Gregorian calendar has a well defined week-numbering system.
 
-let calendar = new Temporal.Calendar("gregory");
+let calendar = "gregory";
 const date = new Temporal.PlainDate(2024, 1, 1, calendar);
 
 assert.sameValue(date.yearOfWeek, 2024);
 
-calendar = new Temporal.Calendar("hebrew");
+calendar = "hebrew";
 const nonisodate = new Temporal.PlainDate(2024, 1, 1, calendar);
 
 assert.sameValue(nonisodate.yearOfWeek, undefined);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/weekOfYear/gregory-iso-weekofyear.js b/test/intl402/Temporal/PlainDateTime/prototype/weekOfYear/gregory-iso-weekofyear.js
index 6f79fd1c11..65f75d4a64 100644
--- a/test/intl402/Temporal/PlainDateTime/prototype/weekOfYear/gregory-iso-weekofyear.js
+++ b/test/intl402/Temporal/PlainDateTime/prototype/weekOfYear/gregory-iso-weekofyear.js
@@ -16,12 +16,12 @@ features: [Temporal]
 
 // 
 
-let calendar = new Temporal.Calendar("gregory");
+let calendar = "gregory";
 const date = new Temporal.PlainDateTime(2021, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
 
 assert.sameValue(date.weekOfYear, 1);
 
-calendar = new Temporal.Calendar("iso8601");
+calendar = "iso8601";
 const isodate = new Temporal.PlainDateTime(2021, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
 
 assert.sameValue(isodate.weekOfYear, 53);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/weekOfYear/non-iso-week-of-year.js b/test/intl402/Temporal/PlainDateTime/prototype/weekOfYear/non-iso-week-of-year.js
index 1eb4e566bb..56077f2e76 100644
--- a/test/intl402/Temporal/PlainDateTime/prototype/weekOfYear/non-iso-week-of-year.js
+++ b/test/intl402/Temporal/PlainDateTime/prototype/weekOfYear/non-iso-week-of-year.js
@@ -11,12 +11,12 @@ features: [Temporal]
 
 // Gregorian calendar has a well defined week-numbering system.
 
-let calendar = new Temporal.Calendar("gregory");
+let calendar = "gregory";
 const date = new Temporal.PlainDateTime(2024, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
 
 assert.sameValue(date.weekOfYear, 1);
 
-calendar = new Temporal.Calendar("hebrew");
+calendar = "hebrew";
 const nonisodate = new Temporal.PlainDateTime(2024, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
 
 assert.sameValue(nonisodate.weekOfYear, undefined);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/yearOfWeek/gregory-iso-weekofyear.js b/test/intl402/Temporal/PlainDateTime/prototype/yearOfWeek/gregory-iso-weekofyear.js
index 63bd715a1b..20034007f9 100644
--- a/test/intl402/Temporal/PlainDateTime/prototype/yearOfWeek/gregory-iso-weekofyear.js
+++ b/test/intl402/Temporal/PlainDateTime/prototype/yearOfWeek/gregory-iso-weekofyear.js
@@ -16,12 +16,12 @@ features: [Temporal]
 
 // 
 
-let calendar = new Temporal.Calendar("gregory");
+let calendar = "gregory";
 const date = new Temporal.PlainDateTime(2021, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
 
 assert.sameValue(date.yearOfWeek, 2021);
 
-calendar = new Temporal.Calendar("iso8601");
+calendar = "iso8601";
 const isodate = new Temporal.PlainDateTime(2021, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
 
 assert.sameValue(isodate.yearOfWeek, 2020);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/yearOfWeek/non-iso-week-of-year.js b/test/intl402/Temporal/PlainDateTime/prototype/yearOfWeek/non-iso-week-of-year.js
index 35c1b13f18..8157aa1414 100644
--- a/test/intl402/Temporal/PlainDateTime/prototype/yearOfWeek/non-iso-week-of-year.js
+++ b/test/intl402/Temporal/PlainDateTime/prototype/yearOfWeek/non-iso-week-of-year.js
@@ -11,12 +11,12 @@ features: [Temporal]
 
 // Gregorian calendar has a well defined week-numbering system.
 
-let calendar = new Temporal.Calendar("gregory");
+let calendar = "gregory";
 const date = new Temporal.PlainDateTime(2024, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
 
 assert.sameValue(date.yearOfWeek, 2024);
 
-calendar = new Temporal.Calendar("hebrew");
+calendar = "hebrew";
 const nonisodate = new Temporal.PlainDateTime(2024, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
 
 assert.sameValue(nonisodate.yearOfWeek, undefined);
diff --git a/test/intl402/Temporal/PlainMonthDay/from/fields-object.js b/test/intl402/Temporal/PlainMonthDay/from/fields-object.js
index 09aaf918da..aa2a4b97ea 100644
--- a/test/intl402/Temporal/PlainMonthDay/from/fields-object.js
+++ b/test/intl402/Temporal/PlainMonthDay/from/fields-object.js
@@ -11,8 +11,6 @@ features: [Temporal]
 const okTests = [
   [{ monthCode: "M08", day: 1, calendar: "gregory" }, "gregory", "monthCode and non-ISO Gregorian string calendar"],
   [{ monthCode: "M08", day: 1, calendar: "hebrew" }, "hebrew", "monthCode and non-ISO non-Gregorian string calendar"],
-  [{ monthCode: "M08", day: 1, calendar: Temporal.Calendar.from("gregory") }, "gregory", "monthCode and non-ISO Gregorian object calendar"],
-  [{ monthCode: "M08", day: 1, calendar: Temporal.Calendar.from("hebrew") }, "hebrew", "monthCode and non-ISO non-Gregorian object calendar"],
 ];
 
 for (const [argument, expectedCalendar, description] of okTests) {
@@ -24,8 +22,6 @@ for (const [argument, expectedCalendar, description] of okTests) {
 const notOkTests = [
   [{ month: 8, day: 1, calendar: "gregory" }, "month and non-ISO string calendar"],
   [{ month: 8, day: 1, calendar: "hebrew" }, "month and non-ISO non-Gregorian string calendar"],
-  [{ month: 8, day: 1, calendar: Temporal.Calendar.from("gregory") }, "month and non-ISO Gregorian object calendar"],
-  [{ month: 8, day: 1, calendar: Temporal.Calendar.from("hebrew") }, "month and non-ISO non-Gregorian object calendar"],
 ];
 
 for (const [argument, description] of notOkTests) {
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/equals/offset-and-iana.js b/test/intl402/Temporal/ZonedDateTime/prototype/equals/offset-and-iana.js
index 8e0d16ea18..548cb7f12c 100644
--- a/test/intl402/Temporal/ZonedDateTime/prototype/equals/offset-and-iana.js
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/equals/offset-and-iana.js
@@ -8,13 +8,8 @@ features: [Temporal]
 ---*/
 
 const zdt = new Temporal.ZonedDateTime(0n, "America/Los_Angeles");
-const otz1 = new Temporal.TimeZone("+05:30");
-const otz2 = new Temporal.TimeZone("+0530");
-const tz = new Temporal.TimeZone("Asia/Kolkata");
-assert(zdt.withTimeZone(otz1).equals(zdt.withTimeZone(otz2)), "+05:30 = +0530");
-assert(zdt.withTimeZone(otz2).equals(zdt.withTimeZone(otz1)), "+0530 = +05:30");
-assert(zdt.withTimeZone(otz1).equals(zdt.withTimeZone("+05:30")), "+05:30 = +05:30 string ID");
-assert(zdt.withTimeZone(otz1).equals(zdt.withTimeZone(otz2).toString()), "+05:30 = +0530 IXDTF string");
-assert(!zdt.withTimeZone(otz1).equals(zdt.withTimeZone("Asia/Kolkata")), "+05:30 != Asia/Kolkata string ID");
-assert(!zdt.withTimeZone(otz1).equals(zdt.withTimeZone(tz)), "+05:30 != Asia/Kolkata");
-assert(!zdt.withTimeZone(otz1).equals(zdt.withTimeZone(tz).toString()), "+05:30 != Asia/Kolkata IXDTF string");
+assert(zdt.withTimeZone("+05:30").equals(zdt.withTimeZone("+0530")), "+05:30 = +0530");
+assert(zdt.withTimeZone("+0530").equals(zdt.withTimeZone("+05:30")), "+0530 = +05:30");
+assert(zdt.withTimeZone("+05:30").equals(zdt.withTimeZone("+0530").toString()), "+05:30 = +0530 IXDTF string");
+assert(!zdt.withTimeZone("+05:30").equals(zdt.withTimeZone("Asia/Kolkata")), "+05:30 != Asia/Kolkata string ID");
+assert(!zdt.withTimeZone("+05:30").equals(zdt.withTimeZone("Asia/Kolkata").toString()), "+05:30 != Asia/Kolkata IXDTF string");
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/equals/sub-minute-offset.js b/test/intl402/Temporal/ZonedDateTime/prototype/equals/sub-minute-offset.js
index fe058b4a7b..0e4bd1173b 100644
--- a/test/intl402/Temporal/ZonedDateTime/prototype/equals/sub-minute-offset.js
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/equals/sub-minute-offset.js
@@ -8,8 +8,7 @@ features: [Temporal]
 ---*/
 
 const expectedNanoseconds = BigInt((44 * 60 + 30) * 1e9);
-const timeZone = new Temporal.TimeZone("Africa/Monrovia");
-const instance = new Temporal.ZonedDateTime(expectedNanoseconds, timeZone);
+const instance = new Temporal.ZonedDateTime(expectedNanoseconds, "Africa/Monrovia");
 
 let result = instance.equals("1970-01-01T00:00:00-00:45[Africa/Monrovia]");
 assert.sameValue(result, true, "UTC offset rounded to minutes is accepted");
@@ -30,6 +29,6 @@ const properties = {
   day: 1,
   minute: 44,
   second: 30,
-  timeZone
+  timeZone: "Africa/Monrovia"
 };
 assert.throws(RangeError, () => instance.equals(properties), "no fuzzy matching is done on offset in property bag");
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/since/sub-minute-offset.js b/test/intl402/Temporal/ZonedDateTime/prototype/since/sub-minute-offset.js
index 775dd0430c..f7cd828947 100644
--- a/test/intl402/Temporal/ZonedDateTime/prototype/since/sub-minute-offset.js
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/since/sub-minute-offset.js
@@ -8,7 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("Africa/Monrovia");
+const timeZone = "Africa/Monrovia";
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
 let result = instance.since("1970-01-01T00:44:30-00:44:30[Africa/Monrovia]");
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/until/sub-minute-offset.js b/test/intl402/Temporal/ZonedDateTime/prototype/until/sub-minute-offset.js
index e108189671..08a6640eb8 100644
--- a/test/intl402/Temporal/ZonedDateTime/prototype/until/sub-minute-offset.js
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/until/sub-minute-offset.js
@@ -8,8 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("Africa/Monrovia");
-const instance = new Temporal.ZonedDateTime(0n, timeZone);
+const instance = new Temporal.ZonedDateTime(0n, "Africa/Monrovia");
 
 let result = instance.until("1970-01-01T00:44:30-00:44:30[Africa/Monrovia]");
 TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 1, 29, 0, 0, 0, 0, "UTC offset rounded to minutes is accepted");
@@ -30,6 +29,6 @@ const properties = {
   day: 1,
   minute: 44,
   second: 30,
-  timeZone
+  timeZone: "Africa/Monrovia"
 };
 assert.throws(RangeError, () => instance.until(properties), "no fuzzy matching is done on offset in property bag");
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/weekOfYear/gregory-iso-weekofyear.js b/test/intl402/Temporal/ZonedDateTime/prototype/weekOfYear/gregory-iso-weekofyear.js
index c02e49a0b4..e9c2477db6 100644
--- a/test/intl402/Temporal/ZonedDateTime/prototype/weekOfYear/gregory-iso-weekofyear.js
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/weekOfYear/gregory-iso-weekofyear.js
@@ -16,12 +16,12 @@ features: [Temporal]
 
 // 
 
-let calendar = new Temporal.Calendar("gregory");
+let calendar = "gregory";
 const date = new Temporal.ZonedDateTime(1_609_504_496_987_654_321n, "UTC", calendar);
 
 assert.sameValue(date.weekOfYear, 1);
 
-calendar = new Temporal.Calendar("iso8601");
+calendar = "iso8601";
 const isodate = new Temporal.ZonedDateTime(1_609_504_496_987_654_321n, "UTC", calendar);
 
 assert.sameValue(isodate.weekOfYear, 53);
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/weekOfYear/non-iso-week-of-year.js b/test/intl402/Temporal/ZonedDateTime/prototype/weekOfYear/non-iso-week-of-year.js
index c5f2394416..eb85685685 100644
--- a/test/intl402/Temporal/ZonedDateTime/prototype/weekOfYear/non-iso-week-of-year.js
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/weekOfYear/non-iso-week-of-year.js
@@ -11,14 +11,14 @@ features: [Temporal]
 
 // Gregorian calendar has a well defined week-numbering system.
 
-let calendar = new Temporal.Calendar("gregory");
+let calendar = "gregory";
 
 // Epoch Nanoseconds for new Temporal.PlainDateTime(2024, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
 const date = new Temporal.ZonedDateTime(1_704_112_496_987_654_321n, "UTC", calendar);
 
 assert.sameValue(date.weekOfYear, 1);
 
-calendar = new Temporal.Calendar("hebrew");
+calendar = "hebrew";
 const nonisodate = new Temporal.ZonedDateTime(1_704_112_496_987_654_321n, "UTC", calendar);
 
 assert.sameValue(nonisodate.weekOfYear, undefined);
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/with/offset-property-sub-minute.js b/test/intl402/Temporal/ZonedDateTime/prototype/with/offset-property-sub-minute.js
index ed5c00b7cf..d1cc633ee2 100644
--- a/test/intl402/Temporal/ZonedDateTime/prototype/with/offset-property-sub-minute.js
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/with/offset-property-sub-minute.js
@@ -8,8 +8,7 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const timeZone = new Temporal.TimeZone("Africa/Monrovia");
-const instance = Temporal.ZonedDateTime.from({ year: 1970, month: 1, day: 1, hour: 12, timeZone });
+const instance = Temporal.ZonedDateTime.from({ year: 1970, month: 1, day: 1, hour: 12, timeZone: "Africa/Monrovia" });
 assert.sameValue(instance.offset, "-00:44:30", "original offset");
 const properties = { day: 2, offset: "-00:45" };
 
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/yearOfWeek/gregory-iso-weekofyear.js b/test/intl402/Temporal/ZonedDateTime/prototype/yearOfWeek/gregory-iso-weekofyear.js
index 439a5173d1..f7b22ab358 100644
--- a/test/intl402/Temporal/ZonedDateTime/prototype/yearOfWeek/gregory-iso-weekofyear.js
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/yearOfWeek/gregory-iso-weekofyear.js
@@ -16,12 +16,12 @@ features: [Temporal]
 
 // 
 
-let calendar = new Temporal.Calendar("gregory");
+let calendar = "gregory";
 const date = new Temporal.ZonedDateTime(1_609_504_496_987_654_321n, "UTC", calendar);
 
 assert.sameValue(date.yearOfWeek, 2021);
 
-calendar = new Temporal.Calendar("iso8601");
+calendar = "iso8601";
 const isodate = new Temporal.ZonedDateTime(1_609_504_496_987_654_321n, "UTC", calendar);
 
 assert.sameValue(isodate.yearOfWeek, 2020);
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/yearOfWeek/non-iso-week-of-year.js b/test/intl402/Temporal/ZonedDateTime/prototype/yearOfWeek/non-iso-week-of-year.js
index 7e163fa529..55e8d624ee 100644
--- a/test/intl402/Temporal/ZonedDateTime/prototype/yearOfWeek/non-iso-week-of-year.js
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/yearOfWeek/non-iso-week-of-year.js
@@ -11,14 +11,14 @@ features: [Temporal]
 
 // Gregorian calendar has a well defined week-numbering system.
 
-let calendar = new Temporal.Calendar("gregory");
+let calendar = "gregory";
 
 // Epoch Nanoseconds for new Temporal.PlainDateTime(2024, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
 const date = new Temporal.ZonedDateTime(1_704_112_496_987_654_321n, "UTC", calendar);
 
 assert.sameValue(date.yearOfWeek, 2024);
 
-calendar = new Temporal.Calendar("hebrew");
+calendar = "hebrew";
 const nonisodate = new Temporal.ZonedDateTime(1_704_112_496_987_654_321n, "UTC", calendar);
 
 assert.sameValue(nonisodate.yearOfWeek, undefined);
diff --git a/test/staging/Temporal/Instant/old/toZonedDateTimeISO.js b/test/staging/Temporal/Instant/old/toZonedDateTimeISO.js
index 95986c44dd..6f50c10771 100644
--- a/test/staging/Temporal/Instant/old/toZonedDateTimeISO.js
+++ b/test/staging/Temporal/Instant/old/toZonedDateTimeISO.js
@@ -13,13 +13,11 @@ var inst = Temporal.Instant.from("1976-11-18T14:23:30.123456789Z");
 assert.throws(TypeError, () => inst.toZonedDateTimeISO());
 
 // time zone parameter UTC
-var tz = Temporal.TimeZone.from("UTC");
-var zdt = inst.toZonedDateTimeISO(tz);
+var zdt = inst.toZonedDateTimeISO("UTC");
 assert.sameValue(inst.epochNanoseconds, zdt.epochNanoseconds);
 assert.sameValue(`${ zdt }`, "1976-11-18T14:23:30.123456789+00:00[UTC]");
 
 // time zone parameter non-UTC
-var tz = Temporal.TimeZone.from("-05:00");
-var zdt = inst.toZonedDateTimeISO(tz);
+var zdt = inst.toZonedDateTimeISO("-05:00");
 assert.sameValue(inst.epochNanoseconds, zdt.epochNanoseconds);
 assert.sameValue(`${ zdt }`, "1976-11-18T09:23:30.123456789-05:00[-05:00]");
diff --git a/test/staging/Temporal/Regex/old/instant.js b/test/staging/Temporal/Regex/old/instant.js
index 09e810ea55..aebde59ffa 100644
--- a/test/staging/Temporal/Regex/old/instant.js
+++ b/test/staging/Temporal/Regex/old/instant.js
@@ -10,8 +10,7 @@ features: [Temporal]
 function test(isoString, components) {
   var [y, mon, d, h = 0, min = 0, s = 0, ms = 0, µs = 0, ns = 0] = components;
   var instant = Temporal.Instant.from(isoString);
-  var utc = Temporal.TimeZone.from("UTC");
-  var datetime = utc.getPlainDateTimeFor(instant);
+  var datetime = instant.toZonedDateTimeISO("UTC");
   assert.sameValue(datetime.year, y);
   assert.sameValue(datetime.month, mon);
   assert.sameValue(datetime.day, d);
diff --git a/test/staging/Temporal/ZonedDateTime/old/construction-and-properties.js b/test/staging/Temporal/ZonedDateTime/old/construction-and-properties.js
index 64442e44e9..d4a071a29f 100644
--- a/test/staging/Temporal/ZonedDateTime/old/construction-and-properties.js
+++ b/test/staging/Temporal/ZonedDateTime/old/construction-and-properties.js
@@ -7,12 +7,11 @@ description: Construction and properties
 features: [Temporal]
 ---*/
 
-var tz = new Temporal.TimeZone("-08:00");
 var epochMillis = Date.UTC(1976, 10, 18, 15, 23, 30, 123);
 var epochNanos = BigInt(epochMillis) * BigInt(1000000) + BigInt(456789);
 
 // works
-var zdt = new Temporal.ZonedDateTime(epochNanos, tz);
+var zdt = new Temporal.ZonedDateTime(epochNanos, "-08:00");
 assert(zdt instanceof Temporal.ZonedDateTime);
 assert.sameValue(typeof zdt, "object");
 assert.sameValue(zdt.toInstant().epochMilliseconds, Date.UTC(1976, 10, 18, 15, 23, 30, 123), "epochMilliseconds");
diff --git a/test/staging/Temporal/ZonedDateTime/old/property-bags.js b/test/staging/Temporal/ZonedDateTime/old/property-bags.js
index 21d3f13452..484b1d769e 100644
--- a/test/staging/Temporal/ZonedDateTime/old/property-bags.js
+++ b/test/staging/Temporal/ZonedDateTime/old/property-bags.js
@@ -8,14 +8,12 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-var lagos = Temporal.TimeZone.from("+01:00");
-
 // can be constructed with monthCode and without month
 assert.sameValue(`${ Temporal.ZonedDateTime.from({
   year: 1976,
   monthCode: "M11",
   day: 18,
-  timeZone: lagos
+  timeZone: "+01:00"
 }) }`, "1976-11-18T00:00:00+01:00[+01:00]");
 
 // can be constructed with month and without monthCode
@@ -23,7 +21,7 @@ assert.sameValue(`${ Temporal.ZonedDateTime.from({
   year: 1976,
   month: 11,
   day: 18,
-  timeZone: lagos
+  timeZone: "+01:00"
 }) }`, "1976-11-18T00:00:00+01:00[+01:00]");
 
 // month and monthCode must agree
@@ -32,7 +30,7 @@ assert.throws(RangeError, () => Temporal.ZonedDateTime.from({
   month: 11,
   monthCode: "M12",
   day: 18,
-  timeZone: lagos
+  timeZone: "+01:00"
 }));
 
 // Temporal.ZonedDateTime.from({}) throws
@@ -44,7 +42,7 @@ assert.throws(TypeError, () => Temporal.ZonedDateTime.from({
   month: undefined,
   monthCode: undefined,
   day: 18,
-  timeZone: lagos
+  timeZone: "+01:00"
 }))
 
 // options may be a function object
@@ -52,7 +50,7 @@ assert.sameValue(`${ Temporal.ZonedDateTime.from({
   year: 1976,
   month: 11,
   day: 18,
-  timeZone: lagos
+  timeZone: "+01:00"
 }, () => {
 }) }`, "1976-11-18T00:00:00+01:00[+01:00]");
 
@@ -61,7 +59,7 @@ assert.throws(TypeError, () => Temporal.ZonedDateTime.from({
   years: 1976,
   months: 11,
   days: 18,
-  timeZone: lagos
+  timeZone: "+01:00"
 }));
 
 // incorrectly-spelled properties are ignored
@@ -69,7 +67,7 @@ assert.sameValue(`${ Temporal.ZonedDateTime.from({
   year: 1976,
   month: 11,
   day: 18,
-  timeZone: lagos,
+  timeZone: "+01:00",
   hours: 12
 }) }`, "1976-11-18T00:00:00+01:00[+01:00]");
 
@@ -91,7 +89,7 @@ assert.sameValue(`${ Temporal.ZonedDateTime.from({
       month: 11,
       day: 18,
       offset: offset,
-      timeZone: Temporal.TimeZone.from("+10:00")
+      timeZone: "+10:00"
     })
   )
 });
@@ -102,7 +100,7 @@ var bad = {
   year: 2019,
   month: 1,
   day: 32,
-  timeZone: lagos
+  timeZone: "+01:00"
 };
 assert.throws(RangeError, () => Temporal.ZonedDateTime.from(bad, { overflow: "reject" }));
 assert.sameValue(`${ Temporal.ZonedDateTime.from(bad) }`, "2019-01-31T00:00:00+01:00[+01:00]");
diff --git a/test/staging/Temporal/ZonedDateTime/old/toPlainDate.js b/test/staging/Temporal/ZonedDateTime/old/toPlainDate.js
index 60cca9273b..2957dfb73e 100644
--- a/test/staging/Temporal/ZonedDateTime/old/toPlainDate.js
+++ b/test/staging/Temporal/ZonedDateTime/old/toPlainDate.js
@@ -7,10 +7,8 @@ description: Temporal.ZonedDateTime.prototype.toPlainDate()
 features: [Temporal]
 ---*/
 
-var tz = new Temporal.TimeZone("-07:00");
-
 // works
-var zdt = Temporal.Instant.from("2019-10-29T09:46:38.271986102Z").toZonedDateTimeISO(tz);
+var zdt = Temporal.Instant.from("2019-10-29T09:46:38.271986102Z").toZonedDateTimeISO("-07:00");
 assert.sameValue(`${ zdt.toPlainDate() }`, "2019-10-29");
 
 // preserves the calendar
diff --git a/test/staging/Temporal/ZonedDateTime/old/toPlainTime.js b/test/staging/Temporal/ZonedDateTime/old/toPlainTime.js
index 8e95119cc5..e932b1413c 100644
--- a/test/staging/Temporal/ZonedDateTime/old/toPlainTime.js
+++ b/test/staging/Temporal/ZonedDateTime/old/toPlainTime.js
@@ -7,8 +7,6 @@ description: Temporal.ZonedDateTime.prototype.toPlainTime()
 features: [Temporal]
 ---*/
 
-var tz = new Temporal.TimeZone("-07:00");
-
 // works
-var zdt = Temporal.Instant.from("2019-10-29T09:46:38.271986102Z").toZonedDateTimeISO(tz);
+var zdt = Temporal.Instant.from("2019-10-29T09:46:38.271986102Z").toZonedDateTimeISO("-07:00");
 assert.sameValue(`${ zdt.toPlainTime() }`, "02:46:38.271986102");