diff --git a/test/built-ins/Temporal/Duration/prototype/round/round-cross-unit-boundary.js b/test/built-ins/Temporal/Duration/prototype/round/round-cross-unit-boundary.js
new file mode 100644
index 0000000000..51870b56c3
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/round/round-cross-unit-boundary.js
@@ -0,0 +1,47 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.round
+description: Rounding can cross unit boundaries up to the implicit largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const relativeTo = new Temporal.PlainDate(2022, 1, 1);
+const roundingMode = "expand";
+
+// Positive, date units
+{
+  const duration = new Temporal.Duration(1, 11, 0, 24);
+  const result = duration.round({ smallestUnit: "months", roundingMode, relativeTo });
+  TemporalHelpers.assertDuration(result, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "1 year 12 months balances to 2 years");
+}
+
+// Negative, date units
+{
+  const duration = new Temporal.Duration(-1, -11, 0, -24);
+  const result = duration.round({ smallestUnit: "months", roundingMode, relativeTo });
+  TemporalHelpers.assertDuration(result, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "-1 year -12 months balances to -2 years");
+}
+
+// Positive, time units
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, 1, 59, 59, 900);
+  const result = duration.round({ smallestUnit: "seconds", roundingMode });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, "1:59:60 balances to 2 hours");
+}
+
+// Negative, time units
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, -1, -59, -59, -900);
+  const result = duration.round({ smallestUnit: "seconds", roundingMode });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, -2, 0, 0, 0, 0, 0, "-1:59:60 balances to -2 hours");
+}
+
+// No balancing if smallest unit is largest unit
+{
+  const duration = new Temporal.Duration(0, 11, 0, 24);
+  const result = duration.round({ smallestUnit: "months", roundingMode, relativeTo });
+  TemporalHelpers.assertDuration(result, 0, 12, 0, 0, 0, 0, 0, 0, 0, 0, "12 months stays as is");
+}
diff --git a/test/built-ins/Temporal/Duration/prototype/toString/round-cross-unit-boundary.js b/test/built-ins/Temporal/Duration/prototype/toString/round-cross-unit-boundary.js
new file mode 100644
index 0000000000..e46999f3be
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/toString/round-cross-unit-boundary.js
@@ -0,0 +1,40 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.tostring
+description: Rounding can cross unit boundaries up to days
+features: [Temporal]
+---*/
+
+const roundingMode = "expand";
+
+// Positive, time units
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, 1, 59, 59, 900);
+  assert.sameValue(duration.toString({ fractionalSecondDigits: 0, roundingMode }), "PT2H0S", "1:59:60 balances to 2 hours");
+}
+
+// Negative, time units
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, -1, -59, -59, -900);
+  assert.sameValue(duration.toString({ fractionalSecondDigits: 0, roundingMode }), "-PT2H0S", "-1:59:60 balances to -2 hours");
+}
+
+// Positive, date and time units
+{
+  const duration = new Temporal.Duration(1, 11, 0, 30, 23, 59, 59, 999, 999, 999);
+  assert.sameValue(duration.toString({ fractionalSecondDigits: 8, roundingMode }), "P1Y11M31DT0.00000000S", "units balance only up to days (positive)");
+}
+
+// Negative, date and time units
+{
+  const duration = new Temporal.Duration(-1, -11, 0, -30, -23, -59, -59, -999, -999, -999);
+  assert.sameValue(duration.toString({ fractionalSecondDigits: 8, roundingMode }), "-P1Y11M31DT0.00000000S", "units balance only up to days (negative)");
+}
+
+// No balancing if smallest unit is largest unit
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, 0, 0, 59, 900);
+  assert.sameValue(duration.toString({ fractionalSecondDigits: 0, roundingMode }), "PT60S", "60 seconds stays as is");
+}
diff --git a/test/built-ins/Temporal/Instant/prototype/since/round-cross-unit-boundary.js b/test/built-ins/Temporal/Instant/prototype/since/round-cross-unit-boundary.js
new file mode 100644
index 0000000000..eec78d9588
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/prototype/since/round-cross-unit-boundary.js
@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.since
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.Instant(0n);
+const later = new Temporal.Instant(7199_000_000_000n);
+const duration = earlier.since(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, -2, 0, 0, 0, 0, 0, "-1:59 balances to -2 hours");
diff --git a/test/built-ins/Temporal/Instant/prototype/until/round-cross-unit-boundary.js b/test/built-ins/Temporal/Instant/prototype/until/round-cross-unit-boundary.js
new file mode 100644
index 0000000000..1fbf2148dd
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/prototype/until/round-cross-unit-boundary.js
@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.until
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.Instant(0n);
+const later = new Temporal.Instant(7199_000_000_000n);
+const duration = earlier.until(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, "1:59 balances to 2 hours");
diff --git a/test/built-ins/Temporal/PlainDate/prototype/since/round-cross-unit-boundary.js b/test/built-ins/Temporal/PlainDate/prototype/since/round-cross-unit-boundary.js
new file mode 100644
index 0000000000..34db4ccac3
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/since/round-cross-unit-boundary.js
@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.since
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.PlainDate(2022, 1, 1);
+const later = new Temporal.PlainDate(2023, 12, 25);
+const duration = earlier.since(later, { largestUnit: "years", smallestUnit: "months", roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "-1 year -11 months balances to -2 years");
diff --git a/test/built-ins/Temporal/PlainDate/prototype/until/round-cross-unit-boundary.js b/test/built-ins/Temporal/PlainDate/prototype/until/round-cross-unit-boundary.js
new file mode 100644
index 0000000000..136ae36a04
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/until/round-cross-unit-boundary.js
@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.until
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.PlainDate(2022, 1, 1);
+const later = new Temporal.PlainDate(2023, 12, 25);
+const duration = earlier.until(later, { largestUnit: "years", smallestUnit: "months", roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "1 year 11 months balances to 2 years");
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/since/round-cross-unit-boundary.js b/test/built-ins/Temporal/PlainDateTime/prototype/since/round-cross-unit-boundary.js
new file mode 100644
index 0000000000..59a453eaba
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/since/round-cross-unit-boundary.js
@@ -0,0 +1,33 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.since
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+// Date units
+{
+  const earlier = new Temporal.PlainDateTime(2022, 1, 1);
+  const later = new Temporal.PlainDateTime(2023, 12, 25);
+  const duration = earlier.since(later, { largestUnit: "years", smallestUnit: "months", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "-1 year -11 months balances to -2 years");
+}
+
+// Time units
+{
+  const earlier = new Temporal.PlainDateTime(2000, 5, 2);
+  const later = new Temporal.PlainDateTime(2000, 5, 2, 1, 59, 59);
+  const duration = earlier.since(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, -2, 0, 0, 0, 0, 0, "-1:59 balances to -2 hours");
+}
+
+// Both
+{
+  const earlier = new Temporal.PlainDateTime(1970, 1, 1);
+  const later = new Temporal.PlainDateTime(1971, 12, 31, 23, 59, 59, 999, 999, 999);
+  const duration = earlier.since(later, { largestUnit: "years", smallestUnit: "microseconds", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "rounding down 1 ns balances to -2 years");
+}
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/until/round-cross-unit-boundary.js b/test/built-ins/Temporal/PlainDateTime/prototype/until/round-cross-unit-boundary.js
new file mode 100644
index 0000000000..24cfb6ce58
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/until/round-cross-unit-boundary.js
@@ -0,0 +1,33 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.until
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+// Date units
+{
+  const earlier = new Temporal.PlainDateTime(2022, 1, 1);
+  const later = new Temporal.PlainDateTime(2023, 12, 25);
+  const duration = earlier.until(later, { largestUnit: "years", smallestUnit: "months", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "1 year 11 months balances to 2 years");
+}
+
+// Time units
+{
+  const earlier = new Temporal.PlainDateTime(2000, 5, 2);
+  const later = new Temporal.PlainDateTime(2000, 5, 2, 1, 59, 59);
+  const duration = earlier.until(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, "1:59 balances to 2 hours");
+}
+
+// Both
+{
+  const earlier = new Temporal.PlainDateTime(1970, 1, 1);
+  const later = new Temporal.PlainDateTime(1971, 12, 31, 23, 59, 59, 999, 999, 999);
+  const duration = earlier.until(later, { largestUnit: "years", smallestUnit: "microseconds", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "rounding up 1 ns balances to 2 years");
+}
diff --git a/test/built-ins/Temporal/PlainTime/prototype/since/round-cross-unit-boundary.js b/test/built-ins/Temporal/PlainTime/prototype/since/round-cross-unit-boundary.js
new file mode 100644
index 0000000000..8d018740a2
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/since/round-cross-unit-boundary.js
@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.since
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.PlainTime();
+const later = new Temporal.PlainTime(1, 59, 59);
+const duration = earlier.since(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, -2, 0, 0, 0, 0, 0, "-1:60 balances to -2 hours");
diff --git a/test/built-ins/Temporal/PlainTime/prototype/until/round-cross-unit-boundary.js b/test/built-ins/Temporal/PlainTime/prototype/until/round-cross-unit-boundary.js
new file mode 100644
index 0000000000..7f5e0a95e7
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/until/round-cross-unit-boundary.js
@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.until
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.PlainTime();
+const later = new Temporal.PlainTime(1, 59, 59);
+const duration = earlier.until(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, "1:60 balances to 2 hours");
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/since/round-cross-unit-boundary.js b/test/built-ins/Temporal/PlainYearMonth/prototype/since/round-cross-unit-boundary.js
new file mode 100644
index 0000000000..06c782ff0d
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/since/round-cross-unit-boundary.js
@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.since
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.PlainYearMonth(2022, 1);
+const later = new Temporal.PlainYearMonth(2023, 12);
+const duration = earlier.since(later, { largestUnit: "years", smallestUnit: "months", roundingIncrement: 3, roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "-1 year -12 months balances to -2 years");
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/until/round-cross-unit-boundary.js b/test/built-ins/Temporal/PlainYearMonth/prototype/until/round-cross-unit-boundary.js
new file mode 100644
index 0000000000..54cb3ac26f
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/until/round-cross-unit-boundary.js
@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.until
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.PlainYearMonth(2022, 1);
+const later = new Temporal.PlainYearMonth(2023, 12);
+const duration = earlier.until(later, { largestUnit: "years", smallestUnit: "months", roundingIncrement: 3, roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "1 year 12 months balances to 2 years");
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/round-cross-unit-boundary.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/round-cross-unit-boundary.js
new file mode 100644
index 0000000000..5063f7afee
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/round-cross-unit-boundary.js
@@ -0,0 +1,33 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.since
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+// Date units
+{
+  const earlier = new Temporal.ZonedDateTime(1640995200_000_000_000n /* = 2022-01-01T00 */, "UTC");
+  const later = new Temporal.ZonedDateTime(1703462400_000_000_000n /* = 2023-12-25T00 */, "UTC");
+  const duration = earlier.since(later, { largestUnit: "years", smallestUnit: "months", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "-1 year -11 months balances to -2 years");
+}
+
+// Time units
+{
+  const earlier = new Temporal.ZonedDateTime(0n, "UTC");
+  const later = new Temporal.ZonedDateTime(7199_000_000_000n, "UTC");
+  const duration = earlier.since(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, -2, 0, 0, 0, 0, 0, "-1:59 balances to -2 hours");
+}
+
+// Both
+{
+  const earlier = new Temporal.ZonedDateTime(0n, "UTC");
+  const later = new Temporal.ZonedDateTime(63071999_999_999_999n /* = 1971-12-31T23:59:59.999999999 */, "UTC");
+  const duration = earlier.since(later, { largestUnit: "years", smallestUnit: "microseconds", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "rounding down 1 ns balances to -2 years");
+}
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/round-cross-unit-boundary.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/round-cross-unit-boundary.js
new file mode 100644
index 0000000000..e6c3f1a360
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/round-cross-unit-boundary.js
@@ -0,0 +1,33 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.until
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+// Date units
+{
+  const earlier = new Temporal.ZonedDateTime(1640995200_000_000_000n /* = 2022-01-01T00 */, "UTC");
+  const later = new Temporal.ZonedDateTime(1703462400_000_000_000n /* = 2023-12-25T00 */, "UTC");
+  const duration = earlier.until(later, { largestUnit: "years", smallestUnit: "months", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "1 year 11 months balances to 2 years");
+}
+
+// Time units
+{
+  const earlier = new Temporal.ZonedDateTime(0n, "UTC");
+  const later = new Temporal.ZonedDateTime(7199_000_000_000n, "UTC");
+  const duration = earlier.until(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, "1:59 balances to 2 hours");
+}
+
+// Both
+{
+  const earlier = new Temporal.ZonedDateTime(0n, "UTC");
+  const later = new Temporal.ZonedDateTime(63071999_999_999_999n /* = 1971-12-31T23:59:59.999999999 */, "UTC");
+  const duration = earlier.until(later, { largestUnit: "years", smallestUnit: "microseconds", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "rounding up 1 ns balances to 2 years");
+}
diff --git a/test/staging/Temporal/Duration/old/toString.js b/test/staging/Temporal/Duration/old/toString.js
index a08ddf020c..99fc1e08db 100644
--- a/test/staging/Temporal/Duration/old/toString.js
+++ b/test/staging/Temporal/Duration/old/toString.js
@@ -23,10 +23,3 @@ var d = Temporal.Duration.from({
   microseconds: Number.MAX_SAFE_INTEGER
 });
 assert.sameValue(`${ d }`, "PT9016206453995.731991S");
-
-// rounding can affect units up to seconds
-var d4 = Temporal.Duration.from("P1Y1M1W1DT23H59M59.999999999S");
-assert.sameValue(d4.toString({
-  fractionalSecondDigits: 8,
-  roundingMode: "halfExpand"
-}), "P1Y1M1W1DT23H59M60.00000000S");