From 3f7a5da91b6a5eb1ac022ce31d719fb0f2da9a56 Mon Sep 17 00:00:00 2001
From: Giampaolo Bellavite <io@gpbl.dev>
Date: Sat, 22 Aug 2026 09:07:39 +0200
Subject: [PATCH] test: cover time zone changes after mount

---
 .../react-day-picker/src/DayPicker.test.tsx   | 27 +++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/packages/react-day-picker/src/DayPicker.test.tsx b/packages/react-day-picker/src/DayPicker.test.tsx
index bc0359837..cbcdbdbcf 100644
--- a/packages/react-day-picker/src/DayPicker.test.tsx
+++ b/packages/react-day-picker/src/DayPicker.test.tsx
@@ -533,6 +533,33 @@ describe("when the `month` is changed programmatically", () => {
   });
 });
 
+describe("when the timeZone changes after mount", () => {
+  const defaultMonth = new Date("2024-01-01T00:30:00.000Z");
+  let rerender: ReturnType<typeof render>["rerender"];
+
+  beforeEach(() => {
+    ({ rerender } = render(
+      <DayPicker defaultMonth={defaultMonth} timeZone="America/New_York" />,
+    ));
+  });
+
+  test("displays the month in the initial time zone", () => {
+    expect(grid("December 2023")).toBeInTheDocument();
+  });
+
+  describe("when the instant falls in the following month in the new time zone", () => {
+    beforeEach(() => {
+      rerender(
+        <DayPicker defaultMonth={defaultMonth} timeZone="Europe/Berlin" />,
+      );
+    });
+
+    test("displays the month in the new time zone", () => {
+      expect(grid("January 2024")).toBeInTheDocument();
+    });
+  });
+});
+
 test("extends the default locale", () => {
   render(
     <DayPicker