📅 Week Number Explorer

// ❌ Avoid: Native Date methods for week calculations
const badWeek = new Date("2026-04-11").getWeek(); // Doesn't exist!

// ✅ Better: Use Day.js with ISO week plugin
import dayjs from 'dayjs';
import isoWeek from 'dayjs/plugin/isoWeek';
dayjs.extend(isoWeek);

const date = dayjs("2026-04-11");
console.log('ISO Week:', date.isoWeek());
console.log('ISO Week Year:', date.isoWeekYear());
console.log('ISO Week String:', `${date.isoWeekYear()}-W${String(date.isoWeek()).padStart(2, '0')}`);

// Check for edge cases
if (date.isoWeekYear() !== date.year()) {
  console.log('⚠️ Edge case: ISO week year differs from calendar year');
}

// ✅ Alternative: Luxon
import { DateTime } from 'luxon';
const dt = DateTime.fromISO("2026-04-11");
console.log('Week Number:', dt.weekNumber);
console.log('Week Year:', dt.weekYear);