MCP Time Server Node

# Monthly Recurrence Behavior Verification **Date**: 2025-01-29 **Libraries**: date-fns@4.1.0, date-fns-tz@3.2.0 ## Key Findings ### 1. Month-End Overflow with `addMonths` - `addMonths` intelligently handles month-end overflow - Jan 31 + 1 month = Feb 29 (in leap year) or Feb 28 (non-leap) - Preserves "last day of month" intent when original day exceeds target month ### 2. `setDate` Behavior with Invalid Days - `setDate(29)` on Feb in leap year: Feb 29 - `setDate(29)` on Feb in non-leap year: Mar 1 (overflows) - `setDate(31)` on 30-day month: Overflows to next month ### 3. DST Transitions - `addMonths` preserves wall clock time across DST - Feb 15 14:30 EST → Mar 15 14:30 EDT (same wall time) ### 4. Implementation Strategy for "31st of Every Month" ```javascript const year = targetDate.getFullYear(); const month = targetDate.getMonth(); const lastDay = new Date(year, month + 1, 0).getDate(); const day = Math.min(requestedDay, lastDay); ``` ## Design Decisions 1. **Month-end dates** (29, 30, 31) should map to last valid day of target month 2. **Mid-month dates** (1-28) should preserve exact day 3. **Time preservation** should work across DST boundaries 4. **Timezone context** must be maintained throughout calculation