fix(frontend): 2月29日を誕生日に設定している場合、平年は3月1日を誕生日として扱うように (#17072)

* fix(frontend): 2月29日を誕生日に設定している場合、平年は3月1日を誕生日として扱うように

* Update Changelog

* add tests

* spdx

packages/frontend/test/is-birthday.test.ts

@@ -0,0 +1,55 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import * as Misskey from 'misskey-js';
+import { describe, test, expect } from 'vitest';
+import { isBirthday } from '@/utility/is-birthday.js';
+
+describe('isBirthday', () => {
+	test('通常の誕生日', () => {
+		const currentDate = new Date('2024-05-15');
+		const result = isBirthday({
+			birthday: '2000-05-15',
+		} as Misskey.entities.UserDetailed, currentDate);
+
+		expect(result).toBe(true);
+	});
+
+	test('誕生日ではない場合', () => {
+		const currentDate = new Date('2024-05-15');
+		const result = isBirthday({
+			birthday: '2000-06-20',
+		} as Misskey.entities.UserDetailed, currentDate);
+
+		expect(result).toBe(false);
+	});
+
+	test('平年に閏日生まれを見た際に3月1日を誕生日とする', () => {
+		const currentDate = new Date('2023-03-01');
+		const result = isBirthday({
+			birthday: '2000-02-29',
+		} as Misskey.entities.UserDetailed, currentDate);
+
+		expect(result).toBe(true);
+	});
+
+	test('閏年に閏日生まれを見た際に2月29日を誕生日とする', () => {
+		const currentDate = new Date('2024-02-29');
+		const result = isBirthday({
+			birthday: '2000-02-29',
+		} as Misskey.entities.UserDetailed, currentDate);
+
+		expect(result).toBe(true);
+	});
+
+	test('閏年に閏日生まれを見た際に3月1日を誕生日としない', () => {
+		const currentDate = new Date('2024-03-01');
+		const result = isBirthday({
+			birthday: '2000-02-29',
+		} as Misskey.entities.UserDetailed, currentDate);
+
+		expect(result).toBe(false);
+	});
+});