diff --git a/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp b/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp
index 72a8046c53..4987e38364 100644
--- a/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp
@@ -1595,7 +1595,7 @@ ThrowCompletionOr<ParsedTimeZoneIdentifier> parse_temporal_time_zone_string(VM&
 
     // 6. If timeZoneResult.[[Z]] is true, return ! ParseTimeZoneIdentifier("UTC").
     if (time_zone_result.z_designator)
-        return MUST(parse_time_zone_identifier(vm, "UTC"sv));
+        return MUST(parse_time_zone_identifier(vm, UTC_TIME_ZONE));
 
     // 7. If timeZoneResult.[[OffsetString]] is not EMPTY, return ? ParseTimeZoneIdentifier(timeZoneResult.[[OffsetString]]).
     if (time_zone_result.offset_string.has_value())
diff --git a/Libraries/LibJS/Runtime/Temporal/Duration.cpp b/Libraries/LibJS/Runtime/Temporal/Duration.cpp
index 1054268198..2bc4a997e7 100644
--- a/Libraries/LibJS/Runtime/Temporal/Duration.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/Duration.cpp
@@ -847,7 +847,7 @@ Crypto::BigFraction total_time_duration(TimeDuration const& time_duration, Unit
 }
 
 // 7.5.33 ComputeNudgeWindow ( sign, duration, originEpochNs, isoDateTime, timeZone, calendar, increment, unit, additionalShift ), https://tc39.es/proposal-temporal/#sec-temporal-computenudgewindow
-ThrowCompletionOr<NudgeWindow> compute_nudge_window(VM& vm, i8 sign, InternalDuration const& duration, Crypto::SignedBigInteger const& origin_epoch_ns, ISODateTime const& iso_date_time, Optional<StringView> time_zone, StringView calendar, u64 increment, Unit unit, bool additional_shift)
+ThrowCompletionOr<NudgeWindow> compute_nudge_window(VM& vm, i8 sign, InternalDuration const& duration, Crypto::SignedBigInteger const& origin_epoch_ns, ISODateTime const& iso_date_time, Optional<String const&> time_zone, StringView calendar, u64 increment, Unit unit, bool additional_shift)
 {
     DateDuration start_duration;
     DateDuration end_duration;
@@ -1004,7 +1004,7 @@ ThrowCompletionOr<NudgeWindow> compute_nudge_window(VM& vm, i8 sign, InternalDur
 }
 
 // 7.5.34 NudgeToCalendarUnit ( sign, duration, originEpochNs, destEpochNs, isoDateTime, timeZone, calendar, increment, unit, roundingMode ), https://tc39.es/proposal-temporal/#sec-temporal-nudgetocalendarunit
-ThrowCompletionOr<CalendarNudgeResult> nudge_to_calendar_unit(VM& vm, i8 sign, InternalDuration const& duration, Crypto::SignedBigInteger const& origin_epoch_ns, Crypto::SignedBigInteger const& dest_epoch_ns, ISODateTime const& iso_date_time, Optional<StringView> time_zone, StringView calendar, u64 increment, Unit unit, RoundingMode rounding_mode)
+ThrowCompletionOr<CalendarNudgeResult> nudge_to_calendar_unit(VM& vm, i8 sign, InternalDuration const& duration, Crypto::SignedBigInteger const& origin_epoch_ns, Crypto::SignedBigInteger const& dest_epoch_ns, ISODateTime const& iso_date_time, Optional<String const&> time_zone, StringView calendar, u64 increment, Unit unit, RoundingMode rounding_mode)
 {
     // 1. Let didExpandCalendarUnit be false.
     auto did_expand_calendar_unit = false;
@@ -1155,7 +1155,7 @@ ThrowCompletionOr<CalendarNudgeResult> nudge_to_calendar_unit(VM& vm, i8 sign, I
 }
 
 // 7.5.35 NudgeToZonedTime ( sign, duration, isoDateTime, timeZone, calendar, increment, unit, roundingMode ), https://tc39.es/proposal-temporal/#sec-temporal-nudgetozonedtime
-ThrowCompletionOr<DurationNudgeResult> nudge_to_zoned_time(VM& vm, i8 sign, InternalDuration const& duration, ISODateTime const& iso_date_time, StringView time_zone, StringView calendar, u64 increment, Unit unit, RoundingMode rounding_mode)
+ThrowCompletionOr<DurationNudgeResult> nudge_to_zoned_time(VM& vm, i8 sign, InternalDuration const& duration, ISODateTime const& iso_date_time, String const& time_zone, StringView calendar, u64 increment, Unit unit, RoundingMode rounding_mode)
 {
     // 1. Let start be ? CalendarDateAdd(calendar, isoDateTime.[[ISODate]], duration.[[Date]], CONSTRAIN).
     auto start = TRY(calendar_date_add(vm, calendar, iso_date_time.iso_date, duration.date, Overflow::Constrain));
@@ -1296,7 +1296,7 @@ ThrowCompletionOr<DurationNudgeResult> nudge_to_day_or_time(VM& vm, InternalDura
 }
 
 // 7.5.37 BubbleRelativeDuration ( sign, duration, nudgedEpochNs, isoDateTime, timeZone, calendar, largestUnit, smallestUnit ), https://tc39.es/proposal-temporal/#sec-temporal-bubblerelativeduration
-ThrowCompletionOr<InternalDuration> bubble_relative_duration(VM& vm, i8 sign, InternalDuration duration, Crypto::SignedBigInteger const& nudged_epoch_ns, ISODateTime const& iso_date_time, Optional<StringView> time_zone, StringView calendar, Unit largest_unit, Unit smallest_unit)
+ThrowCompletionOr<InternalDuration> bubble_relative_duration(VM& vm, i8 sign, InternalDuration duration, Crypto::SignedBigInteger const& nudged_epoch_ns, ISODateTime const& iso_date_time, Optional<String const&> time_zone, StringView calendar, Unit largest_unit, Unit smallest_unit)
 {
     // 1. If smallestUnit is largestUnit, return duration.
     if (smallest_unit == largest_unit)
@@ -1397,7 +1397,7 @@ ThrowCompletionOr<InternalDuration> bubble_relative_duration(VM& vm, i8 sign, In
 }
 
 // 7.5.38 RoundRelativeDuration ( duration, originEpochNs, destEpochNs, isoDateTime, timeZone, calendar, largestUnit, increment, smallestUnit, roundingMode ), https://tc39.es/proposal-temporal/#sec-temporal-roundrelativeduration
-ThrowCompletionOr<InternalDuration> round_relative_duration(VM& vm, InternalDuration duration, Crypto::SignedBigInteger const& origin_epoch_ns, Crypto::SignedBigInteger const& dest_epoch_ns, ISODateTime const& iso_date_time, Optional<StringView> time_zone, StringView calendar, Unit largest_unit, u64 increment, Unit smallest_unit, RoundingMode rounding_mode)
+ThrowCompletionOr<InternalDuration> round_relative_duration(VM& vm, InternalDuration duration, Crypto::SignedBigInteger const& origin_epoch_ns, Crypto::SignedBigInteger const& dest_epoch_ns, ISODateTime const& iso_date_time, Optional<String const&> time_zone, StringView calendar, Unit largest_unit, u64 increment, Unit smallest_unit, RoundingMode rounding_mode)
 {
     // 1. Let irregularLengthUnit be false.
     auto irregular_length_unit = false;
@@ -1451,7 +1451,7 @@ ThrowCompletionOr<InternalDuration> round_relative_duration(VM& vm, InternalDura
 }
 
 // 7.5.39 TotalRelativeDuration ( duration, originEpochNs, destEpochNs, isoDateTime, timeZone, calendar, unit ), https://tc39.es/proposal-temporal/#sec-temporal-totalrelativeduration
-ThrowCompletionOr<Crypto::BigFraction> total_relative_duration(VM& vm, InternalDuration const& duration, Crypto::SignedBigInteger const& origin_epoch_ns, Crypto::SignedBigInteger const& dest_epoch_ns, ISODateTime const& iso_date_time, Optional<StringView> time_zone, StringView calendar, Unit unit)
+ThrowCompletionOr<Crypto::BigFraction> total_relative_duration(VM& vm, InternalDuration const& duration, Crypto::SignedBigInteger const& origin_epoch_ns, Crypto::SignedBigInteger const& dest_epoch_ns, ISODateTime const& iso_date_time, Optional<String const&> time_zone, StringView calendar, Unit unit)
 {
     // 1. If IsCalendarUnit(unit) is true, or timeZone is not UNSET and unit is DAY, then
     if (is_calendar_unit(unit) || (time_zone.has_value() && unit == Unit::Day)) {
diff --git a/Libraries/LibJS/Runtime/Temporal/Duration.h b/Libraries/LibJS/Runtime/Temporal/Duration.h
index e96fddccc1..a16265cd3a 100644
--- a/Libraries/LibJS/Runtime/Temporal/Duration.h
+++ b/Libraries/LibJS/Runtime/Temporal/Duration.h
@@ -1,7 +1,7 @@
 /*
  * Copyright (c) 2021-2023, Linus Groh <linusg@serenityos.org>
  * Copyright (c) 2024, Shannon Booth <shannon@serenityos.org>
- * Copyright (c) 2024, Tim Flynn <trflynn89@ladybird.org>
+ * Copyright (c) 2024-2026, Tim Flynn <trflynn89@ladybird.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -146,13 +146,13 @@ i8 time_duration_sign(TimeDuration const&);
 ThrowCompletionOr<double> date_duration_days(VM&, DateDuration const&, PlainDate const&);
 ThrowCompletionOr<TimeDuration> round_time_duration(VM&, TimeDuration const&, Crypto::UnsignedBigInteger const& increment, Unit, RoundingMode);
 Crypto::BigFraction total_time_duration(TimeDuration const&, Unit);
-ThrowCompletionOr<NudgeWindow> compute_nudge_window(VM&, i8 sign, InternalDuration const&, Crypto::SignedBigInteger const& origin_epoch_ns, ISODateTime const& iso_date_time, Optional<StringView> time_zone, StringView calendar, u64 increment, Unit, bool additional_shift);
-ThrowCompletionOr<CalendarNudgeResult> nudge_to_calendar_unit(VM&, i8 sign, InternalDuration const&, Crypto::SignedBigInteger const& origin_epoch_ns, Crypto::SignedBigInteger const& dest_epoch_ns, ISODateTime const&, Optional<StringView> time_zone, StringView calendar, u64 increment, Unit, RoundingMode);
-ThrowCompletionOr<DurationNudgeResult> nudge_to_zoned_time(VM&, i8 sign, InternalDuration const&, ISODateTime const&, StringView time_zone, StringView calendar, u64 increment, Unit, RoundingMode);
+ThrowCompletionOr<NudgeWindow> compute_nudge_window(VM&, i8 sign, InternalDuration const&, Crypto::SignedBigInteger const& origin_epoch_ns, ISODateTime const& iso_date_time, Optional<String const&> time_zone, StringView calendar, u64 increment, Unit, bool additional_shift);
+ThrowCompletionOr<CalendarNudgeResult> nudge_to_calendar_unit(VM&, i8 sign, InternalDuration const&, Crypto::SignedBigInteger const& origin_epoch_ns, Crypto::SignedBigInteger const& dest_epoch_ns, ISODateTime const&, Optional<String const&> time_zone, StringView calendar, u64 increment, Unit, RoundingMode);
+ThrowCompletionOr<DurationNudgeResult> nudge_to_zoned_time(VM&, i8 sign, InternalDuration const&, ISODateTime const&, String const& time_zone, StringView calendar, u64 increment, Unit, RoundingMode);
 ThrowCompletionOr<DurationNudgeResult> nudge_to_day_or_time(VM&, InternalDuration const&, Crypto::SignedBigInteger const& dest_epoch_ns, Unit largest_unit, u64 increment, Unit smallest_unit, RoundingMode);
-ThrowCompletionOr<InternalDuration> bubble_relative_duration(VM&, i8 sign, InternalDuration, Crypto::SignedBigInteger const& nudged_epoch_ns, ISODateTime const&, Optional<StringView> time_zone, StringView calendar, Unit largest_unit, Unit smallest_unit);
-ThrowCompletionOr<InternalDuration> round_relative_duration(VM&, InternalDuration, Crypto::SignedBigInteger const& origin_epoch_ns, Crypto::SignedBigInteger const& dest_epoch_ns, ISODateTime const&, Optional<StringView> time_zone, StringView calendar, Unit largest_unit, u64 increment, Unit smallest_unit, RoundingMode);
-ThrowCompletionOr<Crypto::BigFraction> total_relative_duration(VM&, InternalDuration const&, Crypto::SignedBigInteger const& origin_epoch_ns, Crypto::SignedBigInteger const& dest_epoch_ns, ISODateTime const&, Optional<StringView> time_zone, StringView calendar, Unit);
+ThrowCompletionOr<InternalDuration> bubble_relative_duration(VM&, i8 sign, InternalDuration, Crypto::SignedBigInteger const& nudged_epoch_ns, ISODateTime const&, Optional<String const&> time_zone, StringView calendar, Unit largest_unit, Unit smallest_unit);
+ThrowCompletionOr<InternalDuration> round_relative_duration(VM&, InternalDuration, Crypto::SignedBigInteger const& origin_epoch_ns, Crypto::SignedBigInteger const& dest_epoch_ns, ISODateTime const&, Optional<String const&> time_zone, StringView calendar, Unit largest_unit, u64 increment, Unit smallest_unit, RoundingMode);
+ThrowCompletionOr<Crypto::BigFraction> total_relative_duration(VM&, InternalDuration const&, Crypto::SignedBigInteger const& origin_epoch_ns, Crypto::SignedBigInteger const& dest_epoch_ns, ISODateTime const&, Optional<String const&> time_zone, StringView calendar, Unit);
 String temporal_duration_to_string(Duration const&, Precision);
 ThrowCompletionOr<GC::Ref<Duration>> add_durations(VM&, ArithmeticOperation, Duration const&, Value);
 
diff --git a/Libraries/LibJS/Runtime/Temporal/Instant.cpp b/Libraries/LibJS/Runtime/Temporal/Instant.cpp
index 13b340b37d..22bea2d42f 100644
--- a/Libraries/LibJS/Runtime/Temporal/Instant.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/Instant.cpp
@@ -201,11 +201,11 @@ Crypto::SignedBigInteger round_temporal_instant(Crypto::SignedBigInteger const&
 }
 
 // 8.5.8 TemporalInstantToString ( instant, timeZone, precision ), https://tc39.es/proposal-temporal/#sec-temporal-temporalinstanttostring
-String temporal_instant_to_string(Instant const& instant, Optional<StringView> time_zone, SecondsStringPrecision::Precision precision)
+String temporal_instant_to_string(Instant const& instant, Optional<String const&> time_zone, SecondsStringPrecision::Precision precision)
 {
     // 1. Let outputTimeZone be timeZone.
     // 2. If outputTimeZone is undefined, set outputTimeZone to "UTC".
-    auto output_time_zone = time_zone.value_or("UTC"sv);
+    auto const& output_time_zone = time_zone.value_or(UTC_TIME_ZONE);
 
     // 3. Let epochNs be instant.[[EpochNanoseconds]].
     auto const& epoch_nanoseconds = instant.epoch_nanoseconds()->big_integer();
diff --git a/Libraries/LibJS/Runtime/Temporal/Instant.h b/Libraries/LibJS/Runtime/Temporal/Instant.h
index 6f87e9bc96..8fcf1e9e6a 100644
--- a/Libraries/LibJS/Runtime/Temporal/Instant.h
+++ b/Libraries/LibJS/Runtime/Temporal/Instant.h
@@ -1,7 +1,7 @@
 /*
  * Copyright (c) 2021-2023, Linus Groh <linusg@serenityos.org>
  * Copyright (c) 2021, Idan Horowitz <idan.horowitz@serenityos.org>
- * Copyright (c) 2024, Tim Flynn <trflynn89@ladybird.org>
+ * Copyright (c) 2024-2026, Tim Flynn <trflynn89@ladybird.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -63,7 +63,7 @@ i8 compare_epoch_nanoseconds(Crypto::SignedBigInteger const& epoch_nanoseconds_o
 ThrowCompletionOr<Crypto::SignedBigInteger> add_instant(VM&, Crypto::SignedBigInteger const& epoch_nanoseconds, TimeDuration const&);
 InternalDuration difference_instant(VM&, Crypto::SignedBigInteger const& nanoseconds1, Crypto::SignedBigInteger const& nanoseconds2, u64 rounding_increment, Unit smallest_unit, RoundingMode);
 Crypto::SignedBigInteger round_temporal_instant(Crypto::SignedBigInteger const& nanoseconds, u64 increment, Unit, RoundingMode);
-String temporal_instant_to_string(Instant const&, Optional<StringView> time_zone, SecondsStringPrecision::Precision);
+String temporal_instant_to_string(Instant const&, Optional<String const&> time_zone, SecondsStringPrecision::Precision);
 ThrowCompletionOr<GC::Ref<Duration>> difference_temporal_instant(VM&, DurationOperation, Instant const&, Value other, Value options);
 ThrowCompletionOr<GC::Ref<Instant>> add_duration_to_instant(VM&, ArithmeticOperation, Instant const&, Value temporal_duration_like);
 
diff --git a/Libraries/LibJS/Runtime/Temporal/InstantPrototype.cpp b/Libraries/LibJS/Runtime/Temporal/InstantPrototype.cpp
index 19f35f0ed2..385ec35eb1 100644
--- a/Libraries/LibJS/Runtime/Temporal/InstantPrototype.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/InstantPrototype.cpp
@@ -276,14 +276,12 @@ JS_DEFINE_NATIVE_FUNCTION(InstantPrototype::to_string)
     if (auto const* unit = smallest_unit.get_pointer<Unit>(); unit && *unit == Unit::Hour)
         return vm.throw_completion<RangeError>(ErrorType::OptionIsNotValidValue, temporal_unit_to_string(*unit), vm.names.smallestUnit);
 
-    String time_zone_buffer;
-    Optional<StringView> time_zone;
+    Optional<String> time_zone;
 
     // 11. If timeZone is not undefined, then
     if (!time_zone_value.is_undefined()) {
         // a. Set timeZone to ? ToTemporalTimeZoneIdentifier(timeZone).
-        time_zone_buffer = TRY(to_temporal_time_zone_identifier(vm, time_zone_value));
-        time_zone = time_zone_buffer;
+        time_zone = TRY(to_temporal_time_zone_identifier(vm, time_zone_value));
     }
 
     // 12. Let precision be ToSecondsStringPrecisionRecord(smallestUnit, digits).
diff --git a/Libraries/LibJS/Runtime/Temporal/TimeZone.cpp b/Libraries/LibJS/Runtime/Temporal/TimeZone.cpp
index db0f00a9a1..6520443a0d 100644
--- a/Libraries/LibJS/Runtime/Temporal/TimeZone.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/TimeZone.cpp
@@ -23,6 +23,8 @@
 
 namespace JS::Temporal {
 
+String UTC_TIME_ZONE = "UTC"_string;
+
 // 11.1.2 GetISOPartsFromEpoch ( epochNanoseconds ), https://tc39.es/proposal-temporal/#sec-temporal-getisopartsfromepoch
 ISODateTime get_iso_parts_from_epoch(Crypto::SignedBigInteger const& epoch_nanoseconds)
 {
@@ -77,7 +79,7 @@ ISODateTime get_iso_parts_from_epoch(Crypto::SignedBigInteger const& epoch_nanos
 }
 
 // 11.1.3 GetNamedTimeZoneNextTransition ( timeZoneIdentifier, epochNanoseconds ), https://tc39.es/proposal-temporal/#sec-temporal-getnamedtimezonenexttransition
-Optional<Crypto::SignedBigInteger> get_named_time_zone_next_transition(StringView time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds)
+Optional<Crypto::SignedBigInteger> get_named_time_zone_next_transition(String const& time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds)
 {
     auto epoch_milliseconds = big_floor(epoch_nanoseconds, NANOSECONDS_PER_MILLISECOND);
     auto time = UnixDateTime::from_milliseconds_since_epoch(clip_bigint_to_sane_time(epoch_milliseconds));
@@ -100,7 +102,7 @@ Optional<Crypto::SignedBigInteger> get_named_time_zone_next_transition(StringVie
 }
 
 // 11.1.4 GetNamedTimeZonePreviousTransition ( timeZoneIdentifier, epochNanoseconds ), https://tc39.es/proposal-temporal/#sec-temporal-getnamedtimezoneprevioustransition
-Optional<Crypto::SignedBigInteger> get_named_time_zone_previous_transition(StringView time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds)
+Optional<Crypto::SignedBigInteger> get_named_time_zone_previous_transition(String const& time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds)
 {
     auto epoch_milliseconds = big_floor(epoch_nanoseconds, NANOSECONDS_PER_MILLISECOND);
     auto time = UnixDateTime::from_milliseconds_since_epoch(clip_bigint_to_sane_time(epoch_milliseconds));
@@ -239,7 +241,7 @@ ThrowCompletionOr<String> to_temporal_time_zone_identifier(VM& vm, StringView te
 }
 
 // 11.1.9 GetOffsetNanosecondsFor ( timeZone, epochNs ), https://tc39.es/proposal-temporal/#sec-temporal-getoffsetnanosecondsfor
-i64 get_offset_nanoseconds_for(StringView time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds)
+i64 get_offset_nanoseconds_for(String const& time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds)
 {
     // 1. Let parseResult be ! ParseTimeZoneIdentifier(timeZone).
     auto parse_result = parse_time_zone_identifier(time_zone);
@@ -253,7 +255,7 @@ i64 get_offset_nanoseconds_for(StringView time_zone, Crypto::SignedBigInteger co
 }
 
 // 11.1.10 GetISODateTimeFor ( timeZone, epochNs ), https://tc39.es/proposal-temporal/#sec-temporal-getisodatetimefor
-ISODateTime get_iso_date_time_for(StringView time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds)
+ISODateTime get_iso_date_time_for(String const& time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds)
 {
     // 1. Let offsetNanoseconds be GetOffsetNanosecondsFor(timeZone, epochNs).
     auto offset_nanoseconds = get_offset_nanoseconds_for(time_zone, epoch_nanoseconds);
@@ -266,7 +268,7 @@ ISODateTime get_iso_date_time_for(StringView time_zone, Crypto::SignedBigInteger
 }
 
 // 11.1.11 GetEpochNanosecondsFor ( timeZone, isoDateTime, disambiguation ), https://tc39.es/proposal-temporal/#sec-temporal-getepochnanosecondsfor
-ThrowCompletionOr<Crypto::SignedBigInteger> get_epoch_nanoseconds_for(VM& vm, StringView time_zone, ISODateTime const& iso_date_time, Disambiguation disambiguation)
+ThrowCompletionOr<Crypto::SignedBigInteger> get_epoch_nanoseconds_for(VM& vm, String const& time_zone, ISODateTime const& iso_date_time, Disambiguation disambiguation)
 {
     // 1. Let possibleEpochNs be ? GetPossibleEpochNanoseconds(timeZone, isoDateTime).
     auto possible_epoch_ns = TRY(get_possible_epoch_nanoseconds(vm, time_zone, iso_date_time));
@@ -276,7 +278,7 @@ ThrowCompletionOr<Crypto::SignedBigInteger> get_epoch_nanoseconds_for(VM& vm, St
 }
 
 // 11.1.12 DisambiguatePossibleEpochNanoseconds ( possibleEpochNs, timeZone, isoDateTime, disambiguation ), https://tc39.es/proposal-temporal/#sec-temporal-disambiguatepossibleepochnanoseconds
-ThrowCompletionOr<Crypto::SignedBigInteger> disambiguate_possible_epoch_nanoseconds(VM& vm, Vector<Crypto::SignedBigInteger> possible_epoch_ns, StringView time_zone, ISODateTime const& iso_date_time, Disambiguation disambiguation)
+ThrowCompletionOr<Crypto::SignedBigInteger> disambiguate_possible_epoch_nanoseconds(VM& vm, Vector<Crypto::SignedBigInteger> possible_epoch_ns, String const& time_zone, ISODateTime const& iso_date_time, Disambiguation disambiguation)
 {
     // 1. Let n be the number of elements in possibleEpochNs.
     auto n = possible_epoch_ns.size();
@@ -316,7 +318,7 @@ ThrowCompletionOr<Crypto::SignedBigInteger> disambiguate_possible_epoch_nanoseco
 }
 
 // 11.1.13 GetPossibleEpochNanoseconds ( timeZone, isoDateTime ), https://tc39.es/proposal-temporal/#sec-temporal-getpossibleepochnanoseconds
-ThrowCompletionOr<Vector<Crypto::SignedBigInteger>> get_possible_epoch_nanoseconds(VM& vm, StringView time_zone, ISODateTime const& iso_date_time)
+ThrowCompletionOr<Vector<Crypto::SignedBigInteger>> get_possible_epoch_nanoseconds(VM& vm, String const& time_zone, ISODateTime const& iso_date_time)
 {
     Vector<Crypto::SignedBigInteger> possible_epoch_nanoseconds;
 
@@ -364,7 +366,7 @@ ThrowCompletionOr<Vector<Crypto::SignedBigInteger>> get_possible_epoch_nanosecon
 }
 
 // 11.1.14 GetStartOfDay ( timeZone, isoDate ), https://tc39.es/proposal-temporal/#sec-temporal-getstartofday
-ThrowCompletionOr<Crypto::SignedBigInteger> get_start_of_day(VM& vm, StringView time_zone, ISODate iso_date)
+ThrowCompletionOr<Crypto::SignedBigInteger> get_start_of_day(VM& vm, String const& time_zone, ISODate iso_date)
 {
     // 1. Let isoDateTime be CombineISODateAndTimeRecord(isoDate, MidnightTimeRecord()).
     auto iso_date_time = combine_iso_date_and_time_record(iso_date, midnight_time_record());
@@ -420,7 +422,7 @@ bool time_zone_equals(StringView one, StringView two)
 }
 
 // 11.1.16 ParseTimeZoneIdentifier ( identifier ), https://tc39.es/proposal-temporal/#sec-parsetimezoneidentifier
-ThrowCompletionOr<ParsedTimeZoneIdentifier> parse_time_zone_identifier(VM& vm, StringView identifier)
+ThrowCompletionOr<ParsedTimeZoneIdentifier> parse_time_zone_identifier(VM& vm, String const& identifier)
 {
     // 1. Let parseResult be ParseText(StringToCodePoints(identifier), TimeZoneIdentifier).
     auto parse_result = parse_iso8601(Production::TimeZoneIdentifier, identifier);
@@ -433,7 +435,7 @@ ThrowCompletionOr<ParsedTimeZoneIdentifier> parse_time_zone_identifier(VM& vm, S
 }
 
 // 11.1.16 ParseTimeZoneIdentifier ( identifier ), https://tc39.es/proposal-temporal/#sec-parsetimezoneidentifier
-ParsedTimeZoneIdentifier parse_time_zone_identifier(StringView identifier)
+ParsedTimeZoneIdentifier parse_time_zone_identifier(String const& identifier)
 {
     // OPTIMIZATION: Some callers can assume that parsing will succeed.
 
diff --git a/Libraries/LibJS/Runtime/Temporal/TimeZone.h b/Libraries/LibJS/Runtime/Temporal/TimeZone.h
index 3dcc47e808..abe49033f6 100644
--- a/Libraries/LibJS/Runtime/Temporal/TimeZone.h
+++ b/Libraries/LibJS/Runtime/Temporal/TimeZone.h
@@ -1,6 +1,6 @@
 /*
  * Copyright (c) 2021-2023, Linus Groh <linusg@serenityos.org>
- * Copyright (c) 2024, Tim Flynn <trflynn89@ladybird.org>
+ * Copyright (c) 2024-2026, Tim Flynn <trflynn89@ladybird.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -17,23 +17,25 @@
 
 namespace JS::Temporal {
 
+extern String UTC_TIME_ZONE;
+
 ISODateTime get_iso_parts_from_epoch(Crypto::SignedBigInteger const& epoch_nanoseconds);
-Optional<Crypto::SignedBigInteger> get_named_time_zone_next_transition(StringView time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds);
-Optional<Crypto::SignedBigInteger> get_named_time_zone_previous_transition(StringView time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds);
+Optional<Crypto::SignedBigInteger> get_named_time_zone_next_transition(String const& time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds);
+Optional<Crypto::SignedBigInteger> get_named_time_zone_previous_transition(String const& time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds);
 String format_offset_time_zone_identifier(i64 offset_minutes, Optional<TimeStyle> = {});
 String format_utc_offset_nanoseconds(i64 offset_nanoseconds);
 String format_date_time_utc_offset_rounded(i64 offset_nanoseconds);
 ThrowCompletionOr<String> to_temporal_time_zone_identifier(VM&, Value temporal_time_zone_like);
-i64 get_offset_nanoseconds_for(StringView time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds);
-ISODateTime get_iso_date_time_for(StringView time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds);
+i64 get_offset_nanoseconds_for(String const& time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds);
+ISODateTime get_iso_date_time_for(String const& time_zone, Crypto::SignedBigInteger const& epoch_nanoseconds);
 ThrowCompletionOr<String> to_temporal_time_zone_identifier(VM&, StringView temporal_time_zone_like);
-ThrowCompletionOr<Crypto::SignedBigInteger> get_epoch_nanoseconds_for(VM&, StringView time_zone, ISODateTime const&, Disambiguation);
-ThrowCompletionOr<Crypto::SignedBigInteger> disambiguate_possible_epoch_nanoseconds(VM&, Vector<Crypto::SignedBigInteger> possible_epoch_ns, StringView time_zone, ISODateTime const&, Disambiguation);
-ThrowCompletionOr<Vector<Crypto::SignedBigInteger>> get_possible_epoch_nanoseconds(VM&, StringView time_zone, ISODateTime const&);
-ThrowCompletionOr<Crypto::SignedBigInteger> get_start_of_day(VM&, StringView time_zone, ISODate);
+ThrowCompletionOr<Crypto::SignedBigInteger> get_epoch_nanoseconds_for(VM&, String const& time_zone, ISODateTime const&, Disambiguation);
+ThrowCompletionOr<Crypto::SignedBigInteger> disambiguate_possible_epoch_nanoseconds(VM&, Vector<Crypto::SignedBigInteger> possible_epoch_ns, String const& time_zone, ISODateTime const&, Disambiguation);
+ThrowCompletionOr<Vector<Crypto::SignedBigInteger>> get_possible_epoch_nanoseconds(VM&, String const& time_zone, ISODateTime const&);
+ThrowCompletionOr<Crypto::SignedBigInteger> get_start_of_day(VM&, String const& time_zone, ISODate);
 bool time_zone_equals(StringView one, StringView two);
-ThrowCompletionOr<ParsedTimeZoneIdentifier> parse_time_zone_identifier(VM&, StringView identifier);
-ParsedTimeZoneIdentifier parse_time_zone_identifier(StringView identifier);
+ThrowCompletionOr<ParsedTimeZoneIdentifier> parse_time_zone_identifier(VM&, String const& identifier);
+ParsedTimeZoneIdentifier parse_time_zone_identifier(String const& identifier);
 ParsedTimeZoneIdentifier parse_time_zone_identifier(ParseResult const&);
 
 }
diff --git a/Libraries/LibJS/Runtime/Temporal/ZonedDateTime.cpp b/Libraries/LibJS/Runtime/Temporal/ZonedDateTime.cpp
index ab18766636..5bd42088cc 100644
--- a/Libraries/LibJS/Runtime/Temporal/ZonedDateTime.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/ZonedDateTime.cpp
@@ -38,7 +38,7 @@ void ZonedDateTime::visit_edges(Cell::Visitor& visitor)
 }
 
 // 6.5.1 InterpretISODateTimeOffset ( isoDate, time, offsetBehaviour, offsetNanoseconds, timeZone, disambiguation, offsetOption, matchBehaviour ), https://tc39.es/proposal-temporal/#sec-temporal-interpretisodatetimeoffset
-ThrowCompletionOr<Crypto::SignedBigInteger> interpret_iso_date_time_offset(VM& vm, ISODate iso_date, Variant<ParsedISODateTime::StartOfDay, Time> const& time_or_start_of_day, OffsetBehavior offset_behavior, double offset_nanoseconds, StringView time_zone, Disambiguation disambiguation, OffsetOption offset_option, MatchBehavior match_behavior)
+ThrowCompletionOr<Crypto::SignedBigInteger> interpret_iso_date_time_offset(VM& vm, ISODate iso_date, Variant<ParsedISODateTime::StartOfDay, Time> const& time_or_start_of_day, OffsetBehavior offset_behavior, double offset_nanoseconds, String const& time_zone, Disambiguation disambiguation, OffsetOption offset_option, MatchBehavior match_behavior)
 {
     // 1. If time is START-OF-DAY, then
     if (time_or_start_of_day.has<ParsedISODateTime::StartOfDay>()) {
@@ -393,7 +393,7 @@ String temporal_zoned_date_time_to_string(ZonedDateTime const& zoned_date_time,
 }
 
 // 6.5.5 AddZonedDateTime ( epochNanoseconds, timeZone, calendar, duration, overflow ), https://tc39.es/proposal-temporal/#sec-temporal-addzoneddatetime
-ThrowCompletionOr<Crypto::SignedBigInteger> add_zoned_date_time(VM& vm, Crypto::SignedBigInteger const& epoch_nanoseconds, StringView time_zone, StringView calendar, InternalDuration const& duration, Overflow overflow)
+ThrowCompletionOr<Crypto::SignedBigInteger> add_zoned_date_time(VM& vm, Crypto::SignedBigInteger const& epoch_nanoseconds, String const& time_zone, StringView calendar, InternalDuration const& duration, Overflow overflow)
 {
     // 1. If DateDurationSign(duration.[[Date]]) = 0, return ? AddInstant(epochNanoseconds, duration.[[Time]]).
     if (date_duration_sign(duration.date) == 0)
@@ -420,7 +420,7 @@ ThrowCompletionOr<Crypto::SignedBigInteger> add_zoned_date_time(VM& vm, Crypto::
 }
 
 // 6.5.6 DifferenceZonedDateTime ( ns1, ns2, timeZone, calendar, largestUnit ), https://tc39.es/proposal-temporal/#sec-temporal-differencezoneddatetime
-ThrowCompletionOr<InternalDuration> difference_zoned_date_time(VM& vm, Crypto::SignedBigInteger const& nanoseconds1, Crypto::SignedBigInteger const& nanoseconds2, StringView time_zone, StringView calendar, Unit largest_unit)
+ThrowCompletionOr<InternalDuration> difference_zoned_date_time(VM& vm, Crypto::SignedBigInteger const& nanoseconds1, Crypto::SignedBigInteger const& nanoseconds2, String const& time_zone, StringView calendar, Unit largest_unit)
 {
     // 1. If ns1 = ns2, return CombineDateAndTimeDuration(ZeroDateDuration(), 0).
     if (nanoseconds1 == nanoseconds2)
@@ -503,7 +503,7 @@ ThrowCompletionOr<InternalDuration> difference_zoned_date_time(VM& vm, Crypto::S
 }
 
 // 6.5.7 DifferenceZonedDateTimeWithRounding ( ns1, ns2, timeZone, calendar, largestUnit, roundingIncrement, smallestUnit, roundingMode ), https://tc39.es/proposal-temporal/#sec-temporal-differencezoneddatetimewithrounding
-ThrowCompletionOr<InternalDuration> difference_zoned_date_time_with_rounding(VM& vm, Crypto::SignedBigInteger const& nanoseconds1, Crypto::SignedBigInteger const& nanoseconds2, StringView time_zone, StringView calendar, Unit largest_unit, u64 rounding_increment, Unit smallest_unit, RoundingMode rounding_mode)
+ThrowCompletionOr<InternalDuration> difference_zoned_date_time_with_rounding(VM& vm, Crypto::SignedBigInteger const& nanoseconds1, Crypto::SignedBigInteger const& nanoseconds2, String const& time_zone, StringView calendar, Unit largest_unit, u64 rounding_increment, Unit smallest_unit, RoundingMode rounding_mode)
 {
     // 1. If TemporalUnitCategory(largestUnit) is TIME, return DifferenceInstant(ns1, ns2, roundingIncrement, smallestUnit, roundingMode).
     if (temporal_unit_category(largest_unit) == UnitCategory::Time)
@@ -524,7 +524,7 @@ ThrowCompletionOr<InternalDuration> difference_zoned_date_time_with_rounding(VM&
 }
 
 // 6.5.8 DifferenceZonedDateTimeWithTotal ( ns1, ns2, timeZone, calendar, unit ), https://tc39.es/proposal-temporal/#sec-temporal-differencezoneddatetimewithtotal
-ThrowCompletionOr<Crypto::BigFraction> difference_zoned_date_time_with_total(VM& vm, Crypto::SignedBigInteger const& nanoseconds1, Crypto::SignedBigInteger const& nanoseconds2, StringView time_zone, StringView calendar, Unit unit)
+ThrowCompletionOr<Crypto::BigFraction> difference_zoned_date_time_with_total(VM& vm, Crypto::SignedBigInteger const& nanoseconds1, Crypto::SignedBigInteger const& nanoseconds2, String const& time_zone, StringView calendar, Unit unit)
 {
     // 1. If TemporalUnitCategory(unit) is TIME, then
     if (temporal_unit_category(unit) == UnitCategory::Time) {
diff --git a/Libraries/LibJS/Runtime/Temporal/ZonedDateTime.h b/Libraries/LibJS/Runtime/Temporal/ZonedDateTime.h
index 45e1544554..ec398772e1 100644
--- a/Libraries/LibJS/Runtime/Temporal/ZonedDateTime.h
+++ b/Libraries/LibJS/Runtime/Temporal/ZonedDateTime.h
@@ -1,6 +1,6 @@
 /*
  * Copyright (c) 2021-2023, Linus Groh <linusg@serenityos.org>
- * Copyright (c) 2024, Tim Flynn <trflynn89@ladybird.org>
+ * Copyright (c) 2024-2026, Tim Flynn <trflynn89@ladybird.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -48,14 +48,14 @@ enum class MatchBehavior {
     MatchMinutes,
 };
 
-ThrowCompletionOr<Crypto::SignedBigInteger> interpret_iso_date_time_offset(VM&, ISODate, Variant<ParsedISODateTime::StartOfDay, Time> const&, OffsetBehavior, double offset_nanoseconds, StringView time_zone, Disambiguation, OffsetOption, MatchBehavior);
+ThrowCompletionOr<Crypto::SignedBigInteger> interpret_iso_date_time_offset(VM&, ISODate, Variant<ParsedISODateTime::StartOfDay, Time> const&, OffsetBehavior, double offset_nanoseconds, String const& time_zone, Disambiguation, OffsetOption, MatchBehavior);
 ThrowCompletionOr<GC::Ref<ZonedDateTime>> to_temporal_zoned_date_time(VM&, Value item, Value options = js_undefined());
 ThrowCompletionOr<GC::Ref<ZonedDateTime>> create_temporal_zoned_date_time(VM&, BigInt const& epoch_nanoseconds, String time_zone, String calendar, GC::Ptr<FunctionObject> new_target = {});
 String temporal_zoned_date_time_to_string(ZonedDateTime const&, SecondsStringPrecision::Precision, ShowCalendar, ShowTimeZoneName, ShowOffset, u64 increment = 1, Unit = Unit::Nanosecond, RoundingMode = RoundingMode::Trunc);
-ThrowCompletionOr<Crypto::SignedBigInteger> add_zoned_date_time(VM&, Crypto::SignedBigInteger const& epoch_nanoseconds, StringView time_zone, StringView calendar, InternalDuration const&, Overflow);
-ThrowCompletionOr<InternalDuration> difference_zoned_date_time(VM&, Crypto::SignedBigInteger const& nanoseconds1, Crypto::SignedBigInteger const& nanoseconds2, StringView time_zone, StringView calendar, Unit largest_unit);
-ThrowCompletionOr<InternalDuration> difference_zoned_date_time_with_rounding(VM&, Crypto::SignedBigInteger const& nanoseconds1, Crypto::SignedBigInteger const& nanoseconds2, StringView time_zone, StringView calendar, Unit largest_unit, u64 rounding_increment, Unit smallest_unit, RoundingMode);
-ThrowCompletionOr<Crypto::BigFraction> difference_zoned_date_time_with_total(VM&, Crypto::SignedBigInteger const& nanoseconds1, Crypto::SignedBigInteger const& nanoseconds2, StringView time_zone, StringView calendar, Unit);
+ThrowCompletionOr<Crypto::SignedBigInteger> add_zoned_date_time(VM&, Crypto::SignedBigInteger const& epoch_nanoseconds, String const& time_zone, StringView calendar, InternalDuration const&, Overflow);
+ThrowCompletionOr<InternalDuration> difference_zoned_date_time(VM&, Crypto::SignedBigInteger const& nanoseconds1, Crypto::SignedBigInteger const& nanoseconds2, String const& time_zone, StringView calendar, Unit largest_unit);
+ThrowCompletionOr<InternalDuration> difference_zoned_date_time_with_rounding(VM&, Crypto::SignedBigInteger const& nanoseconds1, Crypto::SignedBigInteger const& nanoseconds2, String const& time_zone, StringView calendar, Unit largest_unit, u64 rounding_increment, Unit smallest_unit, RoundingMode);
+ThrowCompletionOr<Crypto::BigFraction> difference_zoned_date_time_with_total(VM&, Crypto::SignedBigInteger const& nanoseconds1, Crypto::SignedBigInteger const& nanoseconds2, String const& time_zone, StringView calendar, Unit);
 ThrowCompletionOr<GC::Ref<Duration>> difference_temporal_zoned_date_time(VM&, DurationOperation, ZonedDateTime const&, Value other, Value options);
 ThrowCompletionOr<GC::Ref<ZonedDateTime>> add_duration_to_zoned_date_time(VM&, ArithmeticOperation, ZonedDateTime const&, Value temporal_duration_like, Value options);
 
diff --git a/Libraries/LibJS/Runtime/Temporal/ZonedDateTimeConstructor.cpp b/Libraries/LibJS/Runtime/Temporal/ZonedDateTimeConstructor.cpp
index f6d0f73806..692e77af26 100644
--- a/Libraries/LibJS/Runtime/Temporal/ZonedDateTimeConstructor.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/ZonedDateTimeConstructor.cpp
@@ -1,7 +1,7 @@
 /*
  * Copyright (c) 2021-2023, Linus Groh <linusg@serenityos.org>
  * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
- * Copyright (c) 2024-2025, Tim Flynn <trflynn89@ladybird.org>
+ * Copyright (c) 2024-2026, Tim Flynn <trflynn89@ladybird.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -69,7 +69,7 @@ ThrowCompletionOr<GC::Ref<Object>> ZonedDateTimeConstructor::construct(FunctionO
         return vm.throw_completion<TypeError>(ErrorType::NotAString, time_zone_value);
 
     // 5. Let timeZoneParse be ? ParseTimeZoneIdentifier(timeZone).
-    auto time_zone_parse = TRY(parse_time_zone_identifier(vm, time_zone_value.as_string().utf8_string_view()));
+    auto time_zone_parse = TRY(parse_time_zone_identifier(vm, time_zone_value.as_string().utf8_string()));
 
     String time_zone;