added timezone settings

lib/types.ts

@@ -58,6 +58,9 @@ export const getDefaultSettings = (): Settings => ({
   ui: {
     useNumberFormatting: true,
     useGrouping: true,
+  },
+  system: {
+    timezone: Intl.DateTimeFormat().resolvedOptions().timeZone
   }
 });
 
@@ -77,6 +80,11 @@ export interface UISettings {
   useGrouping: boolean;
 }
 
+export interface SystemSettings {
+  timezone: string;
+}
+
 export interface Settings {
   ui: UISettings;
+  system: SystemSettings;
 }

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')
+    })
+  })
+})

lib/utils.ts

@@ -1,6 +1,16 @@
 import { clsx, type ClassValue } from "clsx"
 import { twMerge } from "tailwind-merge"
+import moment from "moment-timezone"
 
 export function cn(...inputs: ClassValue[]) {
   return twMerge(clsx(inputs))
 }
+
+export function getDateInTimezone(date: Date | string, timezone: string): Date {
+  const m = moment.tz(date, timezone);
+  return new Date(m.format('YYYY-MM-DDTHH:mm:ss.SSS[Z]'));
+}
+
+export function getTodayInTimezone(timezone: string): string {
+  return moment.tz(timezone).format('YYYY-MM-DD');
+}