MCP Time Server Node

# Holiday Calculations with date-fns ## Verified on 2025-07-19 with date-fns ^4.1.0 ### Floating Holiday Calculations Successfully tested calculation of "nth weekday of month" holidays: ```javascript // Get 3rd Monday of January (MLK Day) function getNthWeekdayOfMonth(year, month, weekday, n) { const firstDay = new Date(year, month - 1, 1); const firstDayOfWeek = getDay(firstDay); let daysUntilTarget = weekday - firstDayOfWeek; if (daysUntilTarget < 0) { daysUntilTarget += 7; } const targetDate = addDays(firstDay, daysUntilTarget + (n - 1) * 7); if (targetDate.getMonth() !== month - 1) { return null; // nth occurrence doesn't exist } return targetDate; } ``` Verified dates: - MLK Day 2024: January 15, 2024 ✓ - MLK Day 2025: January 20, 2025 ✓ - Thanksgiving 2024: November 28, 2024 ✓ ### Last Weekday of Month For holidays like Memorial Day (last Monday of May): ```javascript function getLastWeekdayOfMonth(year, month, weekday) { const lastDay = lastDayOfMonth(new Date(year, month - 1)); const lastDayOfWeek = getDay(lastDay); let daysBack = lastDayOfWeek - weekday; if (daysBack < 0) { daysBack += 7; } return addDays(lastDay, -daysBack); } ``` ### Observed Holiday Rules Different countries have different observation rules: **US Federal**: - Saturday → Friday (previous day) - Sunday → Monday (next day) **UK/Canada Bank Holidays**: - Saturday → Monday (next Monday) - Sunday → Monday (next Monday) ### Key Findings 1. **Floating holidays** can be calculated reliably with date-fns 2. **Observation rules** must be per-holiday, not just per-country 3. **Edge cases** include consecutive holidays (UK Christmas/Boxing Day) 4. **Easter** requires special calculation (Computus algorithm) or embedded dates ### Business Day Impact When holidays are observed: - July 4, 2026 (Saturday) → Observed July 3 (Friday) - This changes a business day to a holiday