diff --git a/test/built-ins/Temporal/Duration/compare/precision-exact-mathematical-values-1.js b/test/built-ins/Temporal/Duration/compare/precision-exact-mathematical-values-1.js
new file mode 100644
index 0000000000..f553c5df7d
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/compare/precision-exact-mathematical-values-1.js
@@ -0,0 +1,68 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.compare
+description: >
+  Duration components are precise mathematical integers.
+info: |
+  Temporal.Duration.compare ( one, two [ , options ] )
+
+  ...
+  7. If any of one.[[Years]], two.[[Years]], one.[[Months]], two.[[Months]], one.[[Weeks]], or
+     two.[[Weeks]] are not 0, then
+    a. Let unbalanceResult1 be ? UnbalanceDurationRelative(one.[[Years]], one.[[Months]],
+       one.[[Weeks]], one.[[Days]], "day", relativeTo).
+  ...
+  9. Let ns1 be ! TotalDurationNanoseconds(days1, one.[[Hours]], one.[[Minutes]], one.[[Seconds]],
+     one.[[Milliseconds]], one.[[Microseconds]], one.[[Nanoseconds]], shift1).
+  10. Let ns2 be ! TotalDurationNanoseconds(days2, two.[[Hours]], two.[[Minutes]], two.[[Seconds]],
+      two.[[Milliseconds]], two.[[Microseconds]], two.[[Nanoseconds]], shift2).
+  11. If ns1 > ns2, return 1𝔽.
+  12. If ns1 < ns2, return -1𝔽.
+  13. Return +0𝔽.
+
+  UnbalanceDurationRelative ( years, months, weeks, days, largestUnit, relativeTo )
+
+  ...
+  11. Else,
+    a. If any of years, months, and weeks are not zero, then
+      ...
+      iv. Repeat, while weeks ≠ 0,
+        1. Let moveResult be ? MoveRelativeDate(calendar, relativeTo, oneWeek).
+        2. Set relativeTo to moveResult.[[RelativeTo]].
+        3. Set days to days + moveResult.[[Days]].
+        4. Set weeks to weeks - sign.
+  12. Return ? CreateDateDurationRecord(years, months, weeks, days).
+features: [Temporal]
+---*/
+
+var one = Temporal.Duration.from({
+  days: Number.MAX_SAFE_INTEGER,
+  weeks: 3,
+});
+
+var two = Temporal.Duration.from({
+  days: Number.MAX_SAFE_INTEGER + 3,
+  weeks: 0,
+});
+
+var cal = new class extends Temporal.Calendar {
+  dateAdd(date, duration, options) {
+    // Add one day when one week was requested.
+    if (duration.toString() === "P1W") {
+      return super.dateAdd(date, "P1D", options);
+    }
+
+    // Only expect to add one week.
+    throw new Test262Error("dateAdd called with unexpected value");
+  }
+}("iso8601");
+
+var pd = new Temporal.PlainDate(1970, 1, 1, cal);
+
+// |Number.MAX_SAFE_INTEGER + 1 + 1 + 1| is unequal to |Number.MAX_SAFE_INTEGER + 3|
+// when the addition is performed using IEEE-754 semantics. But for compare we have
+// to ensure exact mathematical computations are performed.
+
+assert.sameValue(Temporal.Duration.compare(one, two, {relativeTo: pd}), 0);
diff --git a/test/built-ins/Temporal/Duration/compare/precision-exact-mathematical-values-2.js b/test/built-ins/Temporal/Duration/compare/precision-exact-mathematical-values-2.js
new file mode 100644
index 0000000000..4c5f817144
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/compare/precision-exact-mathematical-values-2.js
@@ -0,0 +1,68 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.compare
+description: >
+  Duration components are precise mathematical integers.
+info: |
+  Temporal.Duration.compare ( one, two [ , options ] )
+
+  ...
+  7. If any of one.[[Years]], two.[[Years]], one.[[Months]], two.[[Months]], one.[[Weeks]], or
+     two.[[Weeks]] are not 0, then
+    a. Let unbalanceResult1 be ? UnbalanceDurationRelative(one.[[Years]], one.[[Months]],
+       one.[[Weeks]], one.[[Days]], "day", relativeTo).
+  ...
+  9. Let ns1 be ! TotalDurationNanoseconds(days1, one.[[Hours]], one.[[Minutes]], one.[[Seconds]],
+     one.[[Milliseconds]], one.[[Microseconds]], one.[[Nanoseconds]], shift1).
+  10. Let ns2 be ! TotalDurationNanoseconds(days2, two.[[Hours]], two.[[Minutes]], two.[[Seconds]],
+      two.[[Milliseconds]], two.[[Microseconds]], two.[[Nanoseconds]], shift2).
+  11. If ns1 > ns2, return 1𝔽.
+  12. If ns1 < ns2, return -1𝔽.
+  13. Return +0𝔽.
+
+  UnbalanceDurationRelative ( years, months, weeks, days, largestUnit, relativeTo )
+
+  ...
+  11. Else,
+    a. If any of years, months, and weeks are not zero, then
+      ...
+      iv. Repeat, while weeks ≠ 0,
+        1. Let moveResult be ? MoveRelativeDate(calendar, relativeTo, oneWeek).
+        2. Set relativeTo to moveResult.[[RelativeTo]].
+        3. Set days to days + moveResult.[[Days]].
+        4. Set weeks to weeks - sign.
+  12. Return ? CreateDateDurationRecord(years, months, weeks, days).
+features: [Temporal]
+---*/
+
+var one = Temporal.Duration.from({
+  days: Number.MAX_SAFE_INTEGER,
+  weeks: 3,
+});
+
+var two = Temporal.Duration.from({
+  days: Number.MAX_SAFE_INTEGER + 3,
+  weeks: 0,
+});
+
+var cal = new class extends Temporal.Calendar {
+  dateAdd(date, duration, options) {
+    // Add one day when one week was requested.
+    if (duration.toString() === "P1W") {
+      return super.dateAdd(date, "P1D", options);
+    }
+
+    // Use zero duration to avoid a RangeError during CalculateOffsetShift.
+    return super.dateAdd(date, "PT0S", options);
+  }
+}("iso8601");
+
+var zdt = new Temporal.ZonedDateTime(0n, "UTC", cal);
+
+// |Number.MAX_SAFE_INTEGER + 1 + 1 + 1| is unequal to |Number.MAX_SAFE_INTEGER + 3|
+// when the addition is performed using IEEE-754 semantics. But for compare we have
+// to ensure exact mathematical computations are performed.
+
+assert.sameValue(Temporal.Duration.compare(one, two, {relativeTo: zdt}), 0);
diff --git a/test/built-ins/Temporal/Duration/from/argument-string-fractional-precision.js b/test/built-ins/Temporal/Duration/from/argument-string-fractional-precision.js
new file mode 100644
index 0000000000..418c063412
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/from/argument-string-fractional-precision.js
@@ -0,0 +1,56 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.from
+description: >
+  Fractional parts are computed using exact mathematical values.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const tests = {
+  "PT0.999999999H": Temporal.Duration.from({
+    minutes: 59,
+    seconds: 59,
+    milliseconds: 999,
+    microseconds: 996,
+    nanoseconds: 400,
+  }),
+  "PT0.000000011H": Temporal.Duration.from({
+    minutes: 0,
+    seconds: 0,
+    milliseconds: 0,
+    microseconds: 39,
+    nanoseconds: 600,
+  }),
+
+  "PT0.999999999M": Temporal.Duration.from({
+    seconds: 59,
+    milliseconds: 999,
+    microseconds: 999,
+    nanoseconds: 940,
+  }),
+  "PT0.000000011M": Temporal.Duration.from({
+    seconds: 0,
+    milliseconds: 0,
+    microseconds: 0,
+    nanoseconds: 660,
+  }),
+
+  "PT0.999999999S": Temporal.Duration.from({
+    milliseconds: 999,
+    microseconds: 999,
+    nanoseconds: 999,
+  }),
+  "PT0.000000011S": Temporal.Duration.from({
+    milliseconds: 0,
+    microseconds: 0,
+    nanoseconds: 11,
+  }),
+};
+
+for (let [str, expected] of Object.entries(tests)) {
+  let actual = Temporal.Duration.from(str);
+  TemporalHelpers.assertDurationsEqual(actual, expected, str);
+}
diff --git a/test/built-ins/Temporal/Duration/from/argument-string-fractional-with-zero-subparts.js b/test/built-ins/Temporal/Duration/from/argument-string-fractional-with-zero-subparts.js
new file mode 100644
index 0000000000..6e032de1d9
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/from/argument-string-fractional-with-zero-subparts.js
@@ -0,0 +1,33 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.from
+description: >
+  Throws when a fractional unit is present and a sub-part is zero.
+features: [Temporal]
+---*/
+
+const invalid = [
+  // Hours fraction with whole minutes.
+  "PT0.1H0M",
+
+  // Hours fraction with fractional minutes.
+  "PT0.1H0.0M",
+
+  // Hours fraction with whole seconds.
+  "PT0.1H0S",
+
+  // Hours fraction with fractional seconds.
+  "PT0.1H0.0S",
+
+  // Minutes fraction with whole seconds.
+  "PT0.1M0S",
+
+  // Minutes fraction with fractional seconds.
+  "PT0.1M0.0S",
+];
+
+for (let string of invalid) {
+  assert.throws(RangeError, () => Temporal.Duration.from(string));
+}
diff --git a/test/built-ins/Temporal/Duration/prototype/add/nanoseconds-is-number-max-safe-integer.js b/test/built-ins/Temporal/Duration/prototype/add/nanoseconds-is-number-max-safe-integer.js
new file mode 100644
index 0000000000..c888faa6db
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/add/nanoseconds-is-number-max-safe-integer.js
@@ -0,0 +1,57 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.add
+description: >
+  AddDuration computes on exact mathematical number values.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const plainDate = new Temporal.PlainDate(1970, 1, 1);
+const zonedDateTime = new Temporal.ZonedDateTime(0n, "UTC", "iso8601");
+
+// Largest temporal unit is "day".
+const duration1 = Temporal.Duration.from({nanoseconds: Number.MAX_SAFE_INTEGER});
+const duration2 = Temporal.Duration.from({nanoseconds: 2, days: 1});
+const nanos = BigInt(Number.MAX_SAFE_INTEGER) + 2n;
+
+TemporalHelpers.assertDuration(
+  duration1.add(duration2),
+  0, 0, 0,
+  1 + Number((nanos / (24n * 60n * 60n * 1_000_000_000n))),
+  Number((nanos / (60n * 60n * 1_000_000_000n)) % 24n),
+  Number((nanos / (60n * 1_000_000_000n)) % 60n),
+  Number((nanos / 1_000_000_000n) % 60n),
+  Number((nanos / 1_000_000n) % 1000n),
+  Number((nanos / 1000n) % 1000n),
+  Number(nanos % 1000n),
+  "duration1.add(duration2)"
+);
+
+TemporalHelpers.assertDuration(
+  duration1.add(duration2, {relativeTo: plainDate}),
+  0, 0, 0,
+  1 + Number((nanos / (24n * 60n * 60n * 1_000_000_000n))),
+  Number((nanos / (60n * 60n * 1_000_000_000n)) % 24n),
+  Number((nanos / (60n * 1_000_000_000n)) % 60n),
+  Number((nanos / 1_000_000_000n) % 60n),
+  Number((nanos / 1_000_000n) % 1000n),
+  Number((nanos / 1000n) % 1000n),
+  Number(nanos % 1000n),
+  "duration1.add(duration2, {relativeTo: plainDate})"
+);
+
+TemporalHelpers.assertDuration(
+  duration1.add(duration2, {relativeTo: zonedDateTime}),
+  0, 0, 0,
+  1 + Number((nanos / (24n * 60n * 60n * 1_000_000_000n))),
+  Number((nanos / (60n * 60n * 1_000_000_000n)) % 24n),
+  Number((nanos / (60n * 1_000_000_000n)) % 60n),
+  Number((nanos / 1_000_000_000n) % 60n),
+  Number((nanos / 1_000_000n) % 1000n),
+  Number((nanos / 1000n) % 1000n),
+  Number(nanos % 1000n),
+  "duration1.add(duration2, {relativeTo: zonedDateTime})"
+);
diff --git a/test/built-ins/Temporal/Duration/prototype/add/nanoseconds-is-number-max-value-2.js b/test/built-ins/Temporal/Duration/prototype/add/nanoseconds-is-number-max-value-2.js
new file mode 100644
index 0000000000..e7958b9bed
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/add/nanoseconds-is-number-max-value-2.js
@@ -0,0 +1,49 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.add
+description: >
+  BalanceDuration computes on exact mathematical number values.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const plainDate = new Temporal.PlainDate(1970, 1, 1);
+const zonedDateTime = new Temporal.ZonedDateTime(0n, "UTC", "iso8601");
+
+// Largest temporal unit is "day".
+const duration1 = Temporal.Duration.from({nanoseconds: Number.MAX_VALUE});
+const duration2 = Temporal.Duration.from({nanoseconds: Number.MAX_VALUE, days: 1});
+const nanos = BigInt(Number.MAX_VALUE) * 2n;
+
+TemporalHelpers.assertDuration(
+  duration1.add(duration2),
+  0, 0, 0,
+  1 + Number((nanos / (24n * 60n * 60n * 1_000_000_000n))),
+  Number((nanos / (60n * 60n * 1_000_000_000n)) % 24n),
+  Number((nanos / (60n * 1_000_000_000n)) % 60n),
+  Number((nanos / 1_000_000_000n) % 60n),
+  Number((nanos / 1_000_000n) % 1000n),
+  Number((nanos / 1000n) % 1000n),
+  Number(nanos % 1000n),
+  "duration1.add(duration2)"
+);
+
+TemporalHelpers.assertDuration(
+  duration1.add(duration2, {relativeTo: plainDate}),
+  0, 0, 0,
+  1 + Number((nanos / (24n * 60n * 60n * 1_000_000_000n))),
+  Number((nanos / (60n * 60n * 1_000_000_000n)) % 24n),
+  Number((nanos / (60n * 1_000_000_000n)) % 60n),
+  Number((nanos / 1_000_000_000n) % 60n),
+  Number((nanos / 1_000_000n) % 1000n),
+  Number((nanos / 1000n) % 1000n),
+  Number(nanos % 1000n),
+  "duration1.add(duration2, {relativeTo: plainDate})"
+);
+
+// Throws a RangeError because the intermediate instant is too large.
+assert.throws(RangeError, () => {
+  duration1.add(duration2, {relativeTo: zonedDateTime});
+});
diff --git a/test/built-ins/Temporal/Duration/prototype/add/precision-exact-mathematical-values.js b/test/built-ins/Temporal/Duration/prototype/add/precision-exact-mathematical-values.js
new file mode 100644
index 0000000000..9e19c9bc3d
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/add/precision-exact-mathematical-values.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.add
+description: >
+  AddDuration computes on exact mathematical number values.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+// Largest temporal unit is "microsecond".
+let duration1 = Temporal.Duration.from({microseconds: Number.MAX_SAFE_INTEGER + 1, nanoseconds: 0});
+let duration2 = Temporal.Duration.from({microseconds: 1, nanoseconds: 1000});
+
+TemporalHelpers.assertDuration(
+  duration1.add(duration2),
+  0, 0, 0, 0,
+  0, 0, 0, 0,
+  9007199254740994,
+  0,
+  "duration1.add(duration2)"
+);
diff --git a/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-balance-duration-relative-months.js b/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-balance-duration-relative-months.js
new file mode 100644
index 0000000000..0f73af6ca5
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-balance-duration-relative-months.js
@@ -0,0 +1,52 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.round
+description: >
+  BalanceDurationRelative computes on exact mathematical values.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+{
+  let date = new Temporal.PlainDate(1970, 1, 1);
+
+  let duration = Temporal.Duration.from({
+    months: Number.MAX_SAFE_INTEGER,
+    days: 31 + 28 + 31,
+  });
+
+  let result = duration.round({
+    largestUnit: "months",
+    relativeTo: date,
+  });
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 9007199254740994, 0, 0,
+    0, 0, 0,
+    0, 0, 0,
+  );
+}
+
+{
+  let date = new Temporal.PlainDate(1970, 1, 1);
+
+  let duration = Temporal.Duration.from({
+    months: Number.MAX_SAFE_INTEGER,
+    days: 31 + 28 + 31 + 1,
+  });
+
+  let result = duration.round({
+    largestUnit: "months",
+    relativeTo: date,
+  });
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 9007199254740994, 0, 1,
+    0, 0, 0,
+    0, 0, 0,
+  );
+}
diff --git a/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-balance-duration-relative-weeks.js b/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-balance-duration-relative-weeks.js
new file mode 100644
index 0000000000..5d0bf427a3
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-balance-duration-relative-weeks.js
@@ -0,0 +1,52 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.round
+description: >
+  BalanceDurationRelative computes on exact mathematical values.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+{
+  let date = new Temporal.PlainDate(1970, 1, 1);
+
+  let duration = Temporal.Duration.from({
+    weeks: Number.MAX_SAFE_INTEGER,
+    days: 7 * 3,
+  });
+
+  let result = duration.round({
+    largestUnit: "weeks",
+    relativeTo: date,
+  });
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 0, 9007199254740994, 0,
+    0, 0, 0,
+    0, 0, 0,
+  );
+}
+
+{
+  let date = new Temporal.PlainDate(1970, 1, 1);
+
+  let duration = Temporal.Duration.from({
+    weeks: Number.MAX_SAFE_INTEGER,
+    days: 7 * 3 + 1,
+  });
+
+  let result = duration.round({
+    largestUnit: "weeks",
+    relativeTo: date,
+  });
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 0, 9007199254740994, 1,
+    0, 0, 0,
+    0, 0, 0,
+  );
+}
diff --git a/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-balance-duration-relative-years-days.js b/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-balance-duration-relative-years-days.js
new file mode 100644
index 0000000000..cdc53562a1
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-balance-duration-relative-years-days.js
@@ -0,0 +1,52 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.round
+description: >
+  BalanceDurationRelative computes on exact mathematical values.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+{
+  let date = new Temporal.PlainDate(1970, 1, 1);
+
+  let duration = Temporal.Duration.from({
+    years: Number.MAX_SAFE_INTEGER,
+    days: 366 + 365 + 365,
+  });
+
+  let result = duration.round({
+    largestUnit: "years",
+    relativeTo: date,
+  });
+
+  TemporalHelpers.assertDuration(
+    result,
+    9007199254740994, 0, 0, 0,
+    0, 0, 0,
+    0, 0, 0,
+  );
+}
+
+{
+  let date = new Temporal.PlainDate(1970, 1, 1);
+
+  let duration = Temporal.Duration.from({
+    years: Number.MAX_SAFE_INTEGER,
+    days: 366 + 365 + 365 + 1,
+  });
+
+  let result = duration.round({
+    largestUnit: "years",
+    relativeTo: date,
+  });
+
+  TemporalHelpers.assertDuration(
+    result,
+    9007199254740994, 0, 0, 1,
+    0, 0, 0,
+    0, 0, 0,
+  );
+}
diff --git a/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-balance-duration-relative-years-months.js b/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-balance-duration-relative-years-months.js
new file mode 100644
index 0000000000..16dec1a5db
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-balance-duration-relative-years-months.js
@@ -0,0 +1,52 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.round
+description: >
+  BalanceDurationRelative computes on exact mathematical values.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+{
+  let date = new Temporal.PlainDate(1970, 1, 1);
+
+  let duration = Temporal.Duration.from({
+    years: Number.MAX_SAFE_INTEGER,
+    months: 12 * 3,
+  });
+
+  let result = duration.round({
+    largestUnit: "years",
+    relativeTo: date,
+  });
+
+  TemporalHelpers.assertDuration(
+    result,
+    9007199254740994, 0, 0, 0,
+    0, 0, 0,
+    0, 0, 0,
+  );
+}
+
+{
+  let date = new Temporal.PlainDate(1970, 1, 1);
+
+  let duration = Temporal.Duration.from({
+    years: Number.MAX_SAFE_INTEGER,
+    months: 12 * 3 + 1,
+  });
+
+  let result = duration.round({
+    largestUnit: "years",
+    relativeTo: date,
+  });
+
+  TemporalHelpers.assertDuration(
+    result,
+    9007199254740994, 1, 0, 0,
+    0, 0, 0,
+    0, 0, 0,
+  );
+}
diff --git a/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-balance-duration-relative-years-with-calendar.js b/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-balance-duration-relative-years-with-calendar.js
new file mode 100644
index 0000000000..0afd469096
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-balance-duration-relative-years-with-calendar.js
@@ -0,0 +1,53 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.round
+description: >
+  BalanceDurationRelative computes on exact mathematical values.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+let calendar = new class extends Temporal.Calendar {
+  #dateUntil = 0;
+  dateUntil(one, two, options) {
+    this.#dateUntil++;
+
+    // Subtract one six times from 9007199254740996.
+    if (this.#dateUntil <= 6) {
+      return Temporal.Duration.from({months: 1});
+    }
+
+    // After subtracting six in total, months is 9007199254740996 - 6 = 9007199254740990.
+    // |MAX_SAFE_INTEGER| = 9007199254740991 is larger than 9007199254740990, so we exit
+    // from the loop.
+    if (this.#dateUntil === 7) {
+      return Temporal.Duration.from({months: Number.MAX_SAFE_INTEGER});
+    }
+
+    // Any additional calls to dateUntil are incorrect.
+    throw new Test262Error("dateUntil called more times than expected");
+  }
+}("iso8601");
+
+let date = new Temporal.PlainDate(1970, 1, 1, calendar);
+
+let duration = Temporal.Duration.from({
+  years: 0,
+  months: Number.MAX_SAFE_INTEGER + 4, // 9007199254740996
+});
+
+let result = duration.round({
+  largestUnit: "years",
+  relativeTo: date,
+});
+
+// Years is equal to the number of times we returned one month from dateUntil.
+// Months is equal to 9007199254740996 - 6.
+TemporalHelpers.assertDuration(
+  result,
+  6, 9007199254740990, 0, 0,
+  0, 0, 0,
+  0, 0, 0,
+);
diff --git a/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-round-duration.js b/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-round-duration.js
new file mode 100644
index 0000000000..c03ca57acc
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/round/precision-exact-in-round-duration.js
@@ -0,0 +1,50 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.round
+description: >
+  RoundDuration computes on exact mathematical values.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+{
+  let duration = Temporal.Duration.from({
+    hours: 100_000,
+    nanoseconds: 5,
+  });
+
+  let rounded = duration.round({smallestUnit: "hours", roundingMode: "ceil"});
+
+  // If RoundDuration() was implemented with float64, precision loss would lead
+  // to computing an incorrect result.
+  //
+  // "PT100000H" with float64, but "PT100001H" with exact mathematical values.
+  TemporalHelpers.assertDuration(
+    rounded,
+    0, 0, 0, 0,
+    100001, 0, 0,
+    0, 0, 0,
+  );
+}
+
+{
+  let duration = Temporal.Duration.from({
+    days: 1000,
+    nanoseconds: 5,
+  });
+
+  let rounded = duration.round({smallestUnit: "days", roundingMode: "ceil"});
+
+  // If RoundDuration() was implemented with float64, precision loss would lead
+  // to computing an incorrect result.
+  //
+  // "P1000D" with float64, but "P1001D" with exact mathematical values.
+  TemporalHelpers.assertDuration(
+    rounded,
+    0, 0, 0, 1001,
+    0, 0, 0,
+    0, 0, 0,
+  );
+}
diff --git a/test/built-ins/Temporal/Duration/prototype/subtract/nanoseconds-is-number-max-safe-integer.js b/test/built-ins/Temporal/Duration/prototype/subtract/nanoseconds-is-number-max-safe-integer.js
new file mode 100644
index 0000000000..34f8b85c71
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/subtract/nanoseconds-is-number-max-safe-integer.js
@@ -0,0 +1,57 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.subtract
+description: >
+  AddDuration computes on exact mathematical number values.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const plainDate = new Temporal.PlainDate(1970, 1, 1);
+const zonedDateTime = new Temporal.ZonedDateTime(0n, "UTC", "iso8601");
+
+// Largest temporal unit is "day".
+const duration1 = Temporal.Duration.from({nanoseconds: Number.MAX_SAFE_INTEGER});
+const duration2 = Temporal.Duration.from({nanoseconds: -2, days: -1});
+const nanos = BigInt(Number.MAX_SAFE_INTEGER) + 2n;
+
+TemporalHelpers.assertDuration(
+  duration1.subtract(duration2),
+  0, 0, 0,
+  1 + Number((nanos / (24n * 60n * 60n * 1_000_000_000n))),
+  Number((nanos / (60n * 60n * 1_000_000_000n)) % 24n),
+  Number((nanos / (60n * 1_000_000_000n)) % 60n),
+  Number((nanos / 1_000_000_000n) % 60n),
+  Number((nanos / 1_000_000n) % 1000n),
+  Number((nanos / 1000n) % 1000n),
+  Number(nanos % 1000n),
+  "duration1.subtract(duration2)"
+);
+
+TemporalHelpers.assertDuration(
+  duration1.subtract(duration2, {relativeTo: plainDate}),
+  0, 0, 0,
+  1 + Number((nanos / (24n * 60n * 60n * 1_000_000_000n))),
+  Number((nanos / (60n * 60n * 1_000_000_000n)) % 24n),
+  Number((nanos / (60n * 1_000_000_000n)) % 60n),
+  Number((nanos / 1_000_000_000n) % 60n),
+  Number((nanos / 1_000_000n) % 1000n),
+  Number((nanos / 1000n) % 1000n),
+  Number(nanos % 1000n),
+  "duration1.subtract(duration2, {relativeTo: plainDate})"
+);
+
+TemporalHelpers.assertDuration(
+  duration1.subtract(duration2, {relativeTo: zonedDateTime}),
+  0, 0, 0,
+  1 + Number((nanos / (24n * 60n * 60n * 1_000_000_000n))),
+  Number((nanos / (60n * 60n * 1_000_000_000n)) % 24n),
+  Number((nanos / (60n * 1_000_000_000n)) % 60n),
+  Number((nanos / 1_000_000_000n) % 60n),
+  Number((nanos / 1_000_000n) % 1000n),
+  Number((nanos / 1000n) % 1000n),
+  Number(nanos % 1000n),
+  "duration1.subtract(duration2, {relativeTo: zonedDateTime})"
+);
diff --git a/test/built-ins/Temporal/Duration/prototype/subtract/nanoseconds-is-number-max-value-2.js b/test/built-ins/Temporal/Duration/prototype/subtract/nanoseconds-is-number-max-value-2.js
new file mode 100644
index 0000000000..ae2e909a25
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/subtract/nanoseconds-is-number-max-value-2.js
@@ -0,0 +1,49 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.subtract
+description: >
+  BalanceDuration computes on exact mathematical number values.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const plainDate = new Temporal.PlainDate(1970, 1, 1);
+const zonedDateTime = new Temporal.ZonedDateTime(0n, "UTC", "iso8601");
+
+// Largest temporal unit is "day".
+const duration1 = Temporal.Duration.from({nanoseconds: Number.MAX_VALUE});
+const duration2 = Temporal.Duration.from({nanoseconds: -Number.MAX_VALUE, days: -1});
+const nanos = BigInt(Number.MAX_VALUE) * 2n;
+
+TemporalHelpers.assertDuration(
+  duration1.subtract(duration2),
+  0, 0, 0,
+  1 + Number((nanos / (24n * 60n * 60n * 1_000_000_000n))),
+  Number((nanos / (60n * 60n * 1_000_000_000n)) % 24n),
+  Number((nanos / (60n * 1_000_000_000n)) % 60n),
+  Number((nanos / 1_000_000_000n) % 60n),
+  Number((nanos / 1_000_000n) % 1000n),
+  Number((nanos / 1000n) % 1000n),
+  Number(nanos % 1000n),
+  "duration1.subtract(duration2)"
+);
+
+TemporalHelpers.assertDuration(
+  duration1.subtract(duration2, {relativeTo: plainDate}),
+  0, 0, 0,
+  1 + Number((nanos / (24n * 60n * 60n * 1_000_000_000n))),
+  Number((nanos / (60n * 60n * 1_000_000_000n)) % 24n),
+  Number((nanos / (60n * 1_000_000_000n)) % 60n),
+  Number((nanos / 1_000_000_000n) % 60n),
+  Number((nanos / 1_000_000n) % 1000n),
+  Number((nanos / 1000n) % 1000n),
+  Number(nanos % 1000n),
+  "duration1.subtract(duration2, {relativeTo: plainDate})"
+);
+
+// Throws a RangeError because the intermediate instant is too large.
+assert.throws(RangeError, () => {
+  duration1.subtract(duration2, {relativeTo: zonedDateTime});
+});
diff --git a/test/built-ins/Temporal/Duration/prototype/subtract/precision-exact-mathematical-values.js b/test/built-ins/Temporal/Duration/prototype/subtract/precision-exact-mathematical-values.js
new file mode 100644
index 0000000000..0f88a3ec8f
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/subtract/precision-exact-mathematical-values.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.subtract
+description: >
+  AddDuration computes on exact mathematical number values.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+// Largest temporal unit is "microsecond".
+let duration1 = Temporal.Duration.from({microseconds: Number.MAX_SAFE_INTEGER + 1, nanoseconds: 0});
+let duration2 = Temporal.Duration.from({microseconds: -1, nanoseconds: -1000});
+
+TemporalHelpers.assertDuration(
+  duration1.subtract(duration2),
+  0, 0, 0, 0,
+  0, 0, 0, 0,
+  9007199254740994,
+  0,
+  "duration1.subtract(duration2)"
+);
diff --git a/test/built-ins/Temporal/Duration/prototype/toString/precision-exact-mathematical-values.js b/test/built-ins/Temporal/Duration/prototype/toString/precision-exact-mathematical-values.js
new file mode 100644
index 0000000000..bf7bc7e1e5
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/toString/precision-exact-mathematical-values.js
@@ -0,0 +1,36 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal-temporaldurationtostring
+description: >
+  Duration components are precise mathematical integers.
+info: |
+  TemporalDurationToString ( years, months, weeks, days, hours, minutes, seconds, milliseconds,
+                             microseconds, nanoseconds, precision )
+  ...
+  2. Set microseconds to microseconds + RoundTowardsZero(nanoseconds / 1000).
+  3. Set nanoseconds to remainder(nanoseconds, 1000).
+  4. Set milliseconds to milliseconds + RoundTowardsZero(microseconds / 1000).
+  5. Set microseconds to remainder(microseconds, 1000).
+  6. Set seconds to seconds + RoundTowardsZero(milliseconds / 1000).
+  7. Set milliseconds to remainder(milliseconds, 1000).
+  ...
+features: [Temporal]
+---*/
+
+{
+  let d = Temporal.Duration.from({microseconds: 10000000000000004000, nanoseconds: 1000});
+
+  // "PT10000000000000.004096S" with float64.
+  // "PT10000000000000.004097S" with exact precision.
+  assert.sameValue(d.toString(), "PT10000000000000.004097S");
+}
+
+{
+  let d = Temporal.Duration.from({seconds: 10000000000000004000, microseconds: 1000});
+
+  // "PT10000000000000004000.001S" with float64.
+  // "PT10000000000000004096.001S" with exact precision.
+  assert.sameValue(d.toString(), "PT10000000000000004096.001S");
+}
diff --git a/test/built-ins/Temporal/PlainTime/prototype/add/precision-exact-mathematical-values-1.js b/test/built-ins/Temporal/PlainTime/prototype/add/precision-exact-mathematical-values-1.js
new file mode 100644
index 0000000000..b56bb1d719
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/add/precision-exact-mathematical-values-1.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.add
+description: >
+  Duration components are precise mathematical integers.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+let duration = Temporal.Duration.from({
+  microseconds: Number.MAX_SAFE_INTEGER,
+  nanoseconds: 1000,
+});
+
+let time = Temporal.PlainTime.from({
+  microsecond: 1,
+});
+
+let result = time.add(duration);
+
+TemporalHelpers.assertPlainTime(result, 23, 47, 34, 740, 993, 0);
diff --git a/test/built-ins/Temporal/PlainTime/prototype/add/precision-exact-mathematical-values-2.js b/test/built-ins/Temporal/PlainTime/prototype/add/precision-exact-mathematical-values-2.js
new file mode 100644
index 0000000000..d86e38e8f6
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/add/precision-exact-mathematical-values-2.js
@@ -0,0 +1,21 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.add
+description: >
+  Duration components are precise mathematical integers.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+let duration = Temporal.Duration.from({
+  hours: Number.MAX_VALUE,
+  minutes: Number.MAX_VALUE,
+});
+
+let time = new Temporal.PlainTime(0, 0, 0, 0, 0, 0);
+
+let result = time.add(duration);
+
+TemporalHelpers.assertPlainTime(result, 10, 8, 0, 0, 0, 0);
diff --git a/test/built-ins/Temporal/PlainTime/prototype/add/precision-exact-mathematical-values-3.js b/test/built-ins/Temporal/PlainTime/prototype/add/precision-exact-mathematical-values-3.js
new file mode 100644
index 0000000000..79161ac477
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/add/precision-exact-mathematical-values-3.js
@@ -0,0 +1,25 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.add
+description: >
+  Duration components are precise mathematical integers.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+let duration = Temporal.Duration.from({
+  hours: Number.MAX_VALUE,
+  minutes: Number.MAX_VALUE,
+  seconds: Number.MAX_VALUE,
+  milliseconds: Number.MAX_VALUE,
+  microseconds: Number.MAX_VALUE,
+  nanoseconds: Number.MAX_VALUE,
+});
+
+let time = new Temporal.PlainTime(0, 0, 0, 0, 0, 0);
+
+let result = time.add(duration);
+
+TemporalHelpers.assertPlainTime(result, 3, 53, 35, 351, 226, 368);
diff --git a/test/built-ins/Temporal/PlainTime/prototype/subtract/precision-exact-mathematical-values-1.js b/test/built-ins/Temporal/PlainTime/prototype/subtract/precision-exact-mathematical-values-1.js
new file mode 100644
index 0000000000..a88c00ae2a
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/subtract/precision-exact-mathematical-values-1.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.subtract
+description: >
+  Duration components are precise mathematical integers.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+let duration = Temporal.Duration.from({
+  microseconds: Number.MIN_SAFE_INTEGER,
+  nanoseconds: -1000,
+});
+
+let time = Temporal.PlainTime.from({
+  microsecond: 1,
+});
+
+let result = time.subtract(duration);
+
+TemporalHelpers.assertPlainTime(result, 23, 47, 34, 740, 993, 0);
diff --git a/test/built-ins/Temporal/PlainTime/prototype/subtract/precision-exact-mathematical-values-2.js b/test/built-ins/Temporal/PlainTime/prototype/subtract/precision-exact-mathematical-values-2.js
new file mode 100644
index 0000000000..0a5ad0d5d2
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/subtract/precision-exact-mathematical-values-2.js
@@ -0,0 +1,21 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.subtract
+description: >
+  Duration components are precise mathematical integers.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+let duration = Temporal.Duration.from({
+  hours: -Number.MAX_VALUE,
+  minutes: -Number.MAX_VALUE,
+});
+
+let time = new Temporal.PlainTime(0, 0, 0, 0, 0, 0);
+
+let result = time.subtract(duration);
+
+TemporalHelpers.assertPlainTime(result, 10, 8, 0, 0, 0, 0);
diff --git a/test/built-ins/Temporal/PlainTime/prototype/subtract/precision-exact-mathematical-values-3.js b/test/built-ins/Temporal/PlainTime/prototype/subtract/precision-exact-mathematical-values-3.js
new file mode 100644
index 0000000000..cda03c1da0
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/subtract/precision-exact-mathematical-values-3.js
@@ -0,0 +1,25 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.subtract
+description: >
+  Duration components are precise mathematical integers.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+let duration = Temporal.Duration.from({
+  hours: -Number.MAX_VALUE,
+  minutes: -Number.MAX_VALUE,
+  seconds: -Number.MAX_VALUE,
+  milliseconds: -Number.MAX_VALUE,
+  microseconds: -Number.MAX_VALUE,
+  nanoseconds: -Number.MAX_VALUE,
+});
+
+let time = new Temporal.PlainTime(0, 0, 0, 0, 0, 0);
+
+let result = time.subtract(duration);
+
+TemporalHelpers.assertPlainTime(result, 3, 53, 35, 351, 226, 368);
diff --git a/test/intl402/Temporal/TimeZone/non-canonical-utc.js b/test/intl402/Temporal/TimeZone/non-canonical-utc.js
new file mode 100644
index 0000000000..f5b125e52f
--- /dev/null
+++ b/test/intl402/Temporal/TimeZone/non-canonical-utc.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone
+description: >
+  TimeZone constructor canonicalises its input.
+features: [Temporal]
+---*/
+
+const testCases = {
+  "Etc/GMT": "UTC",
+  "Etc/GMT+0": "UTC",
+  "Etc/GMT-0": "UTC",
+  "Etc/GMT0": "UTC",
+  "Etc/Greenwich": "UTC",
+  "Etc/UCT": "UTC",
+  "Etc/UTC": "UTC",
+  "Etc/Universal": "UTC",
+  "Etc/Zulu": "UTC",
+};
+
+for (let [id, canonical] of Object.entries(testCases)) {
+  let tz = new Temporal.TimeZone(id);
+
+  assert.sameValue(tz.id, canonical);
+}