From 14cc99071622156785bbec2e8b062c2ce895e154 Mon Sep 17 00:00:00 2001
From: Robert Snow <snowystinger@gmail.com>
Date: Wed, 17 Sep 2025 10:36:03 +1000
Subject: [PATCH 1/3] fix: first day of week bcp 47 parsing in middle of other
 extensions

---
 packages/@internationalized/date/src/queries.ts        | 4 +++-
 packages/@internationalized/date/tests/queries.test.js | 3 +++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/packages/@internationalized/date/src/queries.ts b/packages/@internationalized/date/src/queries.ts
index 732594d729d..151f1bc2731 100644
--- a/packages/@internationalized/date/src/queries.ts
+++ b/packages/@internationalized/date/src/queries.ts
@@ -268,7 +268,9 @@ function getWeekStart(locale: string): number {
     }
     let region = getRegion(locale);
     if (locale.includes('-fw-')) {
-      let day = locale.split('-fw-')[1];
+      // pull the value for the attribute fw from strings such as en-US-u-ca-iso8601-fw-tue or en-US-u-ca-iso8601-fw-mon-nu-thai
+      // where the fw attribute could be followed by another unicode locale extension or not
+      let day = locale.split('-fw-')[1].split('-')[0];
       if (day === 'mon') {
         weekInfo = {firstDay: 1};
       } else if (day === 'tue') {
diff --git a/packages/@internationalized/date/tests/queries.test.js b/packages/@internationalized/date/tests/queries.test.js
index 8ae3f8c3a54..229f2a337df 100644
--- a/packages/@internationalized/date/tests/queries.test.js
+++ b/packages/@internationalized/date/tests/queries.test.js
@@ -281,6 +281,9 @@ describe('queries', function () {
 
       // override first day of week
       expect(startOfWeek(new CalendarDate(2021, 8, 4), 'en-US-u-ca-iso8601-fw-tue')).toEqual(new CalendarDate(2021, 8, 3));
+
+      // override applied if extension appears in the middle of other extensions
+      expect(startOfWeek(new CalendarDate(2021, 8, 4), 'en-US-u-ca-iso8601-fw-tue-nu-thai')).toEqual(new CalendarDate(2021, 8, 3));
     });
   });
 

From 0815c4a50be8e1318b556606c05490a1abf10152 Mon Sep 17 00:00:00 2001
From: Robert Snow <snowystinger@gmail.com>
Date: Wed, 17 Sep 2025 10:41:20 +1000
Subject: [PATCH 2/3] add value to story

---
 packages/react-aria-components/stories/Calendar.stories.tsx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/react-aria-components/stories/Calendar.stories.tsx b/packages/react-aria-components/stories/Calendar.stories.tsx
index 0703be28137..4caa40f4229 100644
--- a/packages/react-aria-components/stories/Calendar.stories.tsx
+++ b/packages/react-aria-components/stories/Calendar.stories.tsx
@@ -161,7 +161,7 @@ export const CalendarFirstDayOfWeekExample: StoryObj<CalendarFirstDayOfWeekExamp
   argTypes: {
     locale: {
       control: 'select',
-      options: ['en-US-u-ca-iso8601-fw-tue', 'en-US-u-ca-iso8601', 'en-US', 'fr-FR-u-ca-iso8601-fw-tue', 'fr-FR-u-ca-iso8601', 'fr-FR']
+      options: ['en-US-u-ca-iso8601-fw-tue', 'en-US-u-ca-iso8601', 'en-US', 'fr-FR-u-ca-iso8601-fw-tue', 'fr-FR-u-ca-iso8601', 'fr-FR', 'en-US-u-ca-iso8601-fw-tue-nu-thai']
     }
   }
 };

From 6de8eee8a45c9baadb11c5b6c35ef49b611ccd97 Mon Sep 17 00:00:00 2001
From: Robert Snow <snowystinger@gmail.com>
Date: Thu, 18 Sep 2025 08:30:21 +1000
Subject: [PATCH 3/3] fix iso8601 case

---
 packages/@internationalized/date/src/queries.ts        | 2 +-
 packages/@internationalized/date/tests/queries.test.js | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/packages/@internationalized/date/src/queries.ts b/packages/@internationalized/date/src/queries.ts
index 151f1bc2731..ce48d95d75c 100644
--- a/packages/@internationalized/date/src/queries.ts
+++ b/packages/@internationalized/date/src/queries.ts
@@ -286,7 +286,7 @@ function getWeekStart(locale: string): number {
       } else {
         weekInfo = {firstDay: 0};
       }
-    } else if (locale.includes('u-ca-iso8601')) {
+    } else if (locale.includes('-ca-iso8601')) {
       weekInfo = {firstDay: 1};
     } else {
       weekInfo = {firstDay: region ? weekStartData[region] || 0 : 0};
diff --git a/packages/@internationalized/date/tests/queries.test.js b/packages/@internationalized/date/tests/queries.test.js
index 229f2a337df..40fceb3494e 100644
--- a/packages/@internationalized/date/tests/queries.test.js
+++ b/packages/@internationalized/date/tests/queries.test.js
@@ -283,6 +283,8 @@ describe('queries', function () {
       expect(startOfWeek(new CalendarDate(2021, 8, 4), 'en-US-u-ca-iso8601-fw-tue')).toEqual(new CalendarDate(2021, 8, 3));
 
       // override applied if extension appears in the middle of other extensions
+      expect(startOfWeek(new CalendarDate(2021, 8, 4), 'en-US-u-nu-thai-ca-iso8601')).toEqual(new CalendarDate(2021, 8, 2));
+      expect(startOfWeek(new CalendarDate(2021, 8, 4), 'en-US-u-nu-thai-ca-iso8601-fw-tue')).toEqual(new CalendarDate(2021, 8, 3));
       expect(startOfWeek(new CalendarDate(2021, 8, 4), 'en-US-u-ca-iso8601-fw-tue-nu-thai')).toEqual(new CalendarDate(2021, 8, 3));
     });
   });