diff --git a/src/objects/js-temporal-objects.cc b/src/objects/js-temporal-objects.cc
index 015b68f600..900d709f20 100644
--- a/src/objects/js-temporal-objects.cc
+++ b/src/objects/js-temporal-objects.cc
@@ -4610,13 +4610,12 @@ class CalendarMap final {
 
 DEFINE_LAZY_LEAKY_OBJECT_GETTER(CalendarMap, GetCalendarMap)
 
-// #sec-temporal-isbuiltincalendar
-bool IsBuiltinCalendar(Isolate* isolate, const std::string& id) {
-  return GetCalendarMap()->Contains(id);
-}
-
 bool IsBuiltinCalendar(Isolate* isolate, Handle<String> id) {
-  return IsBuiltinCalendar(isolate, id->ToCString().get());
+  // 1. Let calendars be AvailableCalendars().
+  // 2. If calendars contains the ASCII-lowercase of id, return true.
+  // 3. Return false.
+  id = Intl::ConvertToLower(isolate, id).ToHandleChecked();
+  return GetCalendarMap()->Contains(id->ToCString().get());
 }
 
 Handle<String> CalendarIdentifier(Isolate* isolate, int32_t index) {
@@ -4625,6 +4624,7 @@ Handle<String> CalendarIdentifier(Isolate* isolate, int32_t index) {
 }
 
 int32_t CalendarIndex(Isolate* isolate, Handle<String> id) {
+  id = Intl::ConvertToLower(isolate, id).ToHandleChecked();
   return GetCalendarMap()->Index(id->ToCString().get());
 }
 
@@ -4645,9 +4645,24 @@ Handle<String> CalendarIdentifier(Isolate* isolate, int32_t index) {
 
 // #sec-temporal-isbuiltincalendar
 bool IsBuiltinCalendar(Isolate* isolate, Handle<String> id) {
-  // 1. If id is not "iso8601", return false.
-  // 2. Return true
-  return isolate->factory()->iso8601_string()->Equals(*id);
+  // Note: For build without intl support, the only item in AvailableCalendars()
+  // is "iso8601".
+  // 1. Let calendars be AvailableCalendars().
+  // 2. If calendars contains the ASCII-lowercase of id, return true.
+  // 3. Return false.
+
+  // Fast path
+  if (isolate->factory()->iso8601_string()->Equals(*id)) return true;
+  if (id->length() != 7) return false;
+  id = String::Flatten(isolate, id);
+
+  DisallowGarbageCollection no_gc;
+  const String::FlatContent& flat = id->GetFlatContent(no_gc);
+  // Return true if id is case insensitive equals to "iso8601".
+  return AsciiAlphaToLower(flat.Get(0)) == 'i' &&
+         AsciiAlphaToLower(flat.Get(1)) == 's' &&
+         AsciiAlphaToLower(flat.Get(2)) == 'o' && flat.Get(3) == '8' &&
+         flat.Get(4) == '6' && flat.Get(5) == '0' && flat.Get(6) == '1';
 }
 
 int32_t CalendarIndex(Isolate* isolate, Handle<String> id) { return 0; }
diff --git a/test/mjsunit/temporal/calendar-constructor.js b/test/mjsunit/temporal/calendar-constructor.js
index d0bf81f56c..12e30236c8 100644
--- a/test/mjsunit/temporal/calendar-constructor.js
+++ b/test/mjsunit/temporal/calendar-constructor.js
@@ -10,7 +10,6 @@ assertThrows(() => Temporal.Calendar("iso8601"), TypeError);
 
 assertThrows(() => new Temporal.Calendar(), RangeError);
 
-// Wrong case
-assertThrows(() => new Temporal.Calendar("ISO8601"), RangeError);
+assertEquals("iso8601", (new Temporal.Calendar("IsO8601")).id)
 
 assertEquals("iso8601", (new Temporal.Calendar("iso8601")).id)
diff --git a/test/test262/test262.status b/test/test262/test262.status
index a168114673..53d54d48b3 100644
--- a/test/test262/test262.status
+++ b/test/test262/test262.status
@@ -427,62 +427,7 @@
   'staging/Intl402/Temporal/old/yearmonth-toLocaleString': [FAIL],
   'staging/Intl402/Temporal/old/zoneddatetime-toLocaleString': [FAIL],
 
-  'built-ins/Temporal/Calendar/from/calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Calendar/prototype/dateAdd/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Calendar/prototype/day/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Calendar/prototype/dayOfWeek/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Calendar/prototype/dayOfYear/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Calendar/prototype/daysInMonth/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Calendar/prototype/daysInWeek/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Calendar/prototype/daysInYear/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Calendar/prototype/inLeapYear/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Calendar/prototype/month/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Calendar/prototype/monthCode/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Calendar/prototype/monthsInYear/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Calendar/prototype/weekOfYear/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Calendar/prototype/year/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Instant/prototype/toZonedDateTime/calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Now/plainDate/calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Now/plainDateTime/calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/Now/zonedDateTime/calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainDate/calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainDate/from/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainDate/prototype/equals/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainDate/prototype/since/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainDate/prototype/until/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainDate/prototype/withCalendar/calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainDateTime/calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainDateTime/from/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainDateTime/prototype/equals/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainDateTime/prototype/since/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainDateTime/prototype/until/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainDateTime/prototype/withCalendar/calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainMonthDay/calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainMonthDay/from/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainMonthDay/prototype/equals/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainTime/prototype/toPlainDateTime/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainTime/prototype/toZonedDateTime/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainYearMonth/calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainYearMonth/from/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainYearMonth/prototype/equals/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainYearMonth/prototype/since/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/PlainYearMonth/prototype/until/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/TimeZone/prototype/getInstantFor/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/TimeZone/prototype/getPlainDateTimeFor/calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/TimeZone/prototype/getPossibleInstantsFor/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/ZonedDateTime/calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/ZonedDateTime/prototype/withCalendar/calendar-case-insensitive': [FAIL],
-  'built-ins/Temporal/ZonedDateTime/prototype/withPlainDate/argument-propertybag-calendar-case-insensitive': [FAIL],
   # intl402
-  'intl402/Temporal/Calendar/calendar-case-insensitive': [FAIL],
-  'intl402/Temporal/Calendar/from/calendar-case-insensitive': [FAIL],
-  'intl402/Temporal/Calendar/prototype/era/argument-propertybag-calendar-case-insensitive': [FAIL],
-  'intl402/Temporal/Calendar/prototype/eraYear/argument-propertybag-calendar-case-insensitive': [FAIL],
   'intl402/Temporal/TimeZone/from/timezone-case-insensitive': [FAIL],
 
   'built-ins/Temporal/Duration/compare/precision-exact-mathematical-values-1': [FAIL],
@@ -514,7 +459,6 @@
   'built-ins/Temporal/ZonedDateTime/prototype/until/roundingmode-ceil': [FAIL],
   'built-ins/Temporal/ZonedDateTime/prototype/until/roundingmode-expand': [FAIL],
   'built-ins/Temporal/ZonedDateTime/prototype/until/roundingmode-floor': [FAIL],
-  'intl402/Temporal/ZonedDateTime/prototype/withCalendar/calendar-case-insensitive': [FAIL],
 
   'built-ins/Temporal/Duration/compare/order-of-operations': [FAIL],
   'built-ins/Temporal/Duration/prototype/round/order-of-operations': [FAIL],