diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-plaindate-calendar-noniso.js b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-plaindate-calendar-noniso.js
new file mode 100644
index 0000000000..118282b48d
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-plaindate-calendar-noniso.js
@@ -0,0 +1,38 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.withplaindate
+description: PlainDate calendar is preserved with ISO PDT
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const cal = {
+  id: 'thisisnotiso',
+  era() { return "the era"; },
+  eraYear() { return 1909; },
+  toString() { return "this is a string"; },
+  year() { return 2008; },
+  month() { return 9; },
+  monthCode() { return "M09"; },
+  day() { return 6; }
+};
+const pdt = new Temporal.PlainDateTime(1995, 12, 7, 3, 24, 30, 0, 0, 0);
+assert.sameValue(pdt.calendar.toString(), "iso8601", "PlainDateTime with ISO calendar");
+const pd = new Temporal.PlainDate(2010, 11, 12, cal);
+const shifted = pdt.withPlainDate(pd);
+
+TemporalHelpers.assertPlainDateTime(
+  shifted,
+  2008, 9, "M09", 6, 3, 24, 30, 0, 0, 0,
+  "calendar is changed if receiver has ISO calendar (1)",
+  "the era",
+  1909
+);
+
+assert.sameValue(
+  shifted.calendar,
+  cal,
+  "calendar is changed if receiver has ISO calendar (2)"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-plaindate-calendar-same-id.js b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-plaindate-calendar-same-id.js
new file mode 100644
index 0000000000..2849905981
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-plaindate-calendar-same-id.js
@@ -0,0 +1,40 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.withplaindate
+description: PlainDate calendar is preserved when both calendars have the same id
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const cal1 = {
+  toString() { return "this is a string"; },
+};
+const cal2 = {
+  id: 'thisisnotiso',
+  era() { return "the era"; },
+  eraYear() { return 1909; },
+  toString() { return "this is a string"; },
+  year() { return 2008; },
+  month() { return 9; },
+  monthCode() { return "M09"; },
+  day() { return 6; }
+};
+const pdt = new Temporal.PlainDateTime(1995, 12, 7, 3, 24, 30, 0, 0, 0, cal1);
+const pd = new Temporal.PlainDate(2010, 11, 12, cal2);
+const shifted = pdt.withPlainDate(pd);
+
+TemporalHelpers.assertPlainDateTime(
+  shifted,
+  2008, 9, "M09", 6, 3, 24, 30, 0, 0, 0,
+  "calendar is changed with same id (1)",
+  "the era",
+  1909
+);
+
+assert.sameValue(
+  shifted.calendar,
+  cal2,
+  "calendar is changed with same id (2)"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-plaindate-calendar-same-object.js b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-plaindate-calendar-same-object.js
new file mode 100644
index 0000000000..f963a3b61d
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-plaindate-calendar-same-object.js
@@ -0,0 +1,42 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.withplaindate
+description: PlainDate calendar is preserved when both calendars are the same object
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+let calls = 0;
+const cal = {
+  id: 'thisisnotiso',
+  era() { return "the era"; },
+  eraYear() { return 1909; },
+  toString() {
+    ++calls;
+    return "this is a string";
+  },
+  year() { return 2008; },
+  month() { return 9; },
+  monthCode() { return "M09"; },
+  day() { return 6; }
+};
+const pdt = new Temporal.PlainDateTime(1995, 12, 7, 3, 24, 30, 0, 0, 0, cal);
+const pd = new Temporal.PlainDate(2010, 11, 12, cal);
+const shifted = pdt.withPlainDate(pd);
+
+TemporalHelpers.assertPlainDateTime(
+  shifted,
+  2008, 9, "M09", 6, 3, 24, 30, 0, 0, 0,
+  "calendar is unchanged with same calendars (1)",
+  "the era",
+  1909
+);
+
+assert.sameValue(
+  shifted.calendar,
+  cal,
+  "calendar is unchanged with same calendars (2)"
+);
+assert.sameValue(calls, 0, "should not have called cal.toString()");
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-plaindate-calendar.js b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-plaindate-calendar.js
new file mode 100644
index 0000000000..ad9f56f7bb
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-plaindate-calendar.js
@@ -0,0 +1,38 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.withplaindate
+description: Original PDT calendar is preserved with ISO PlainDate
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const cal = {
+  id: 'thisisnotiso',
+  era() { return "the era"; },
+  eraYear() { return 1909; },
+  toString() { return "this is a string"; },
+  year() { return 2008; },
+  month() { return 9; },
+  monthCode() { return "M09"; },
+  day() { return 6; }
+};
+const pdt = new Temporal.PlainDateTime(1995, 12, 7, 3, 24, 30, 0, 0, 0, cal);
+const pd = new Temporal.PlainDate(2010, 11, 12);
+assert.sameValue(pd.calendar.toString(), "iso8601", "PlainDate with ISO calendar");
+const shifted = pdt.withPlainDate(pd);
+
+TemporalHelpers.assertPlainDateTime(
+  shifted,
+  2008, 9, "M09", 6, 3, 24, 30, 0, 0, 0,
+  "calendar is unchanged if input has ISO calendar (1)",
+  "the era",
+  1909
+);
+
+assert.sameValue(
+  shifted.calendar,
+  cal,
+  "calendar is unchanged if input has ISO calendar (2)"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-string-iso-calendar.js b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-string-iso-calendar.js
index f3349a95df..888acdca52 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-string-iso-calendar.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-string-iso-calendar.js
@@ -3,7 +3,7 @@
 
 /*---
 esid: sec-temporal.plaindatetime.prototype.withplaindate
-description: New calendar is preserved if original PDT has ISO calendar
+description: Original PDT calendar is preserved with ISO string
 features: [Temporal]
 includes: [temporalHelpers.js]
 ---*/