diff --git a/test/built-ins/Temporal/Instant/compare/no-fractional-minutes-hours.js b/test/built-ins/Temporal/Instant/compare/no-fractional-minutes-hours.js
index 177fe76e085..e9d79dc8c46 100644
--- a/test/built-ins/Temporal/Instant/compare/no-fractional-minutes-hours.js
+++ b/test/built-ins/Temporal/Instant/compare/no-fractional-minutes-hours.js
@@ -8,8 +8,8 @@ features: [Temporal]
 ---*/
 
 const invalidStrings = [
-  ["2025-04-03T05:07.123[CET]", "Fractional minutes"],
-  ["2025-04-03T12.5[CET]", "Fractional hours"],
+  ["2025-04-03T05:07.123[UTC]", "Fractional minutes"],
+  ["2025-04-03T12.5[UTC]", "Fractional hours"],
 ];
 
 for (const [arg, description] of invalidStrings) {
diff --git a/test/built-ins/Temporal/Instant/from/no-fractional-minutes-hours.js b/test/built-ins/Temporal/Instant/from/no-fractional-minutes-hours.js
index 5436c38664b..ad6dfbb6541 100644
--- a/test/built-ins/Temporal/Instant/from/no-fractional-minutes-hours.js
+++ b/test/built-ins/Temporal/Instant/from/no-fractional-minutes-hours.js
@@ -8,8 +8,8 @@ features: [Temporal]
 ---*/
 
 const invalidStrings = [
-  ["2025-04-03T05:07.123[CET]", "Fractional minutes"],
-  ["2025-04-03T12.5[CET]", "Fractional hours"],
+  ["2025-04-03T05:07.123[UTC]", "Fractional minutes"],
+  ["2025-04-03T12.5[UTC]", "Fractional hours"],
 ];
 
 for (const [arg, description] of invalidStrings) {
diff --git a/test/built-ins/Temporal/Instant/prototype/equals/no-fractional-minutes-hours.js b/test/built-ins/Temporal/Instant/prototype/equals/no-fractional-minutes-hours.js
index 812d0318e2c..b7af1fb9d74 100644
--- a/test/built-ins/Temporal/Instant/prototype/equals/no-fractional-minutes-hours.js
+++ b/test/built-ins/Temporal/Instant/prototype/equals/no-fractional-minutes-hours.js
@@ -10,8 +10,8 @@ features: [Temporal]
 const instance = new Temporal.Instant(0n)
 
 const invalidStrings = [
-  ["2025-04-03T05:07.123[CET]", "Fractional minutes"],
-  ["2025-04-03T12.5[CET]", "Fractional hours"],
+  ["2025-04-03T05:07.123[UTC]", "Fractional minutes"],
+  ["2025-04-03T12.5[UTC]", "Fractional hours"],
 ];
 
 for (const [arg, description] of invalidStrings) {
diff --git a/test/built-ins/Temporal/Instant/prototype/since/no-fractional-minutes-hours.js b/test/built-ins/Temporal/Instant/prototype/since/no-fractional-minutes-hours.js
index 49aaf7397c2..2bb1a3b03c6 100644
--- a/test/built-ins/Temporal/Instant/prototype/since/no-fractional-minutes-hours.js
+++ b/test/built-ins/Temporal/Instant/prototype/since/no-fractional-minutes-hours.js
@@ -10,8 +10,8 @@ features: [Temporal]
 const instance = new Temporal.Instant(0n)
 
 const invalidStrings = [
-  ["2025-04-03T05:07.123[CET]", "Fractional minutes"],
-  ["2025-04-03T12.5[CET]", "Fractional hours"],
+  ["2025-04-03T05:07.123[UTC]", "Fractional minutes"],
+  ["2025-04-03T12.5[UTC]", "Fractional hours"],
 ];
 
 for (const [arg, description] of invalidStrings) {
diff --git a/test/built-ins/Temporal/Instant/prototype/until/no-fractional-minutes-hours.js b/test/built-ins/Temporal/Instant/prototype/until/no-fractional-minutes-hours.js
index 02dc829b703..e8ddec34dfc 100644
--- a/test/built-ins/Temporal/Instant/prototype/until/no-fractional-minutes-hours.js
+++ b/test/built-ins/Temporal/Instant/prototype/until/no-fractional-minutes-hours.js
@@ -10,8 +10,8 @@ features: [Temporal]
 const instance = new Temporal.Instant(0n)
 
 const invalidStrings = [
-  ["2025-04-03T05:07.123[CET]", "Fractional minutes"],
-  ["2025-04-03T12.5[CET]", "Fractional hours"],
+  ["2025-04-03T05:07.123[UTC]", "Fractional minutes"],
+  ["2025-04-03T12.5[UTC]", "Fractional hours"],
 ];
 
 for (const [arg, description] of invalidStrings) {
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/no-fractional-minutes-hours.js b/test/built-ins/Temporal/ZonedDateTime/compare/no-fractional-minutes-hours.js
index d3d5a36e232..92667cbe50c 100644
--- a/test/built-ins/Temporal/ZonedDateTime/compare/no-fractional-minutes-hours.js
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/no-fractional-minutes-hours.js
@@ -15,12 +15,12 @@ const invalidStrings = [
 for (const [arg, description] of invalidStrings) {
   assert.throws(
     RangeError,
-      () => Temporal.ZonedDateTime.compare(arg, new Temporal.ZonedDateTime(0n, "CET")),
+      () => Temporal.ZonedDateTime.compare(arg, new Temporal.ZonedDateTime(0n, "UTC")),
     `${description} not allowed in time string (first argument)`
   );
   assert.throws(
     RangeError,
-      () => Temporal.ZonedDateTime.compare(new Temporal.ZonedDateTime(0n, "CET"), arg),
+      () => Temporal.ZonedDateTime.compare(new Temporal.ZonedDateTime(0n, "UTC"), arg),
     `${description} not allowed in time string (second argument)`
   );
 }
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/no-fractional-minutes-hours.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/no-fractional-minutes-hours.js
index 171fa925a36..c0f6a3b98f1 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/no-fractional-minutes-hours.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/no-fractional-minutes-hours.js
@@ -7,7 +7,7 @@ description: Fractional minutes or hours in time string should throw RangeError
 features: [Temporal]
 ---*/
 
-const instance = new Temporal.ZonedDateTime(0n, "CET")
+const instance = new Temporal.ZonedDateTime(0n, "UTC")
 
 const invalidStrings = [
   ["2025-04-03T05:07.123", "Fractional minutes"],
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/no-fractional-minutes-hours.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/no-fractional-minutes-hours.js
index a67e53d064b..d3f420b55ce 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/no-fractional-minutes-hours.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/no-fractional-minutes-hours.js
@@ -7,7 +7,7 @@ description: Fractional minutes or hours in time string should throw RangeError
 features: [Temporal]
 ---*/
 
-const instance = new Temporal.ZonedDateTime(0n, "CET")
+const instance = new Temporal.ZonedDateTime(0n, "UTC")
 
 const invalidStrings = [
   ["2025-04-03T05:07.123", "Fractional minutes"],
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/no-fractional-minutes-hours.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/no-fractional-minutes-hours.js
index ba28f7b3607..e70a462e444 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/no-fractional-minutes-hours.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/no-fractional-minutes-hours.js
@@ -7,7 +7,7 @@ description: Fractional minutes or hours in time string should throw RangeError
 features: [Temporal]
 ---*/
 
-const instance = new Temporal.ZonedDateTime(0n, "CET")
+const instance = new Temporal.ZonedDateTime(0n, "UTC")
 
 const invalidStrings = [
   ["2025-04-03T05:07.123", "Fractional minutes"],