added timezone settings

lib/utils.test.ts

@@ -0,0 +1,50 @@
+import { expect, test, describe, beforeAll, afterAll } from "bun:test";
+import { cn, getDateInTimezone, getTodayInTimezone } from './utils'
+
+describe('cn utility', () => {
+  test('should merge class names correctly', () => {
+    expect(cn('foo', 'bar')).toBe('foo bar')
+    expect(cn('foo', { bar: true })).toBe('foo bar')
+    expect(cn('foo', { bar: false })).toBe('foo')
+    expect(cn('foo', ['bar', 'baz'])).toBe('foo bar baz')
+  })
+})
+
+describe('timezone utilities', () => {
+  describe('getDateInTimezone', () => {
+    test('should convert date to specified timezone', () => {
+      const date = new Date('2024-01-01T00:00:00Z')
+      
+      // Test with specific timezones
+      const nyDate = getDateInTimezone(date, 'America/New_York')
+      expect(nyDate.toISOString()).toBe('2023-12-31T19:00:00.000Z') // NY is UTC-5
+
+      const tokyoDate = getDateInTimezone(date, 'Asia/Tokyo')
+      expect(tokyoDate.toISOString()).toBe('2024-01-01T09:00:00.000Z') // Tokyo is UTC+9
+    })
+
+    test('should handle string dates', () => {
+      const dateStr = '2024-01-01T00:00:00Z'
+      const nyDate = getDateInTimezone(dateStr, 'America/New_York')
+      expect(nyDate.toISOString()).toBe('2023-12-31T19:00:00.000Z')
+    })
+  })
+
+  describe('getTodayInTimezone', () => {
+    let originalDate: Date;
+
+    beforeAll(() => {
+      originalDate = new Date();
+      globalThis.Date.now = () => new Date('2024-01-01T00:00:00Z').getTime();
+    })
+
+    afterAll(() => {
+      globalThis.Date.now = () => originalDate.getTime();
+    })
+
+    test('should return today in YYYY-MM-DD format for timezone', () => {
+      expect(getTodayInTimezone('America/New_York')).toBe('2023-12-31')
+      expect(getTodayInTimezone('Asia/Tokyo')).toBe('2024-01-01')
+    })
+  })
+})