Calendar Accuracy

Verify all date-related claims before including them in responses. Never guess dates or days of week—calendar calculations are error-prone for LLMs.

Examples

• "What day of the week is January 29, 2025?" → Run python scripts/date_calc.py weekday 2025-01-29
• "What's the date 30 days from now?" → Run python scripts/date_calc.py add today 30 days
• "How many days until Christmas?" → Run python scripts/date_calc.py diff today 2025-12-25
• "When are the holidays this year?" → Run python scripts/date_calc.py holidays
• "What are US holidays in 2025?" → Run python scripts/date_calc.py holidays 2025 --country US
• "List the dates for next week" → Run python scripts/date_calc.py range 2025-02-03 2025-02-09

Guidelines

• Always verify date claims using scripts/date_calc.py before responding
• State full dates with day of week: "Wednesday, January 29, 2025"
• For countdowns, show both the count and the target date
• Acknowledge ambiguity in relative expressions ("next Friday" can mean different things)
• Double-check edge cases: leap years, month-end arithmetic, week numbers

Script Usage

# Full date information
python scripts/date_calc.py info 2025-01-29

# Add/subtract time
python scripts/date_calc.py add 2025-01-29 30 days
python scripts/date_calc.py add 2025-01-29 -2 weeks
python scripts/date_calc.py add 2025-01-29 3 months

# Difference between dates
python scripts/date_calc.py diff 2025-01-01 2025-12-31

# Date range listing
python scripts/date_calc.py range 2025-01-01 2025-01-07

# Holidays (defaults to current year, TW)
python scripts/date_calc.py holidays
python scripts/date_calc.py holidays 2025
python scripts/date_calc.py holidays --country US
python scripts/date_calc.py holidays 2025 --country JP
python scripts/date_calc.py holidays --country list  # Show all supported countries

# Day of week only
python scripts/date_calc.py weekday "March 15, 2025"

Common Errors to Avoid

• Month arithmetic overflow: Jan 31 + 1 month → Feb 28/29, not Feb 31
• Leap year assumptions: Always verify if Feb 29 exists in the year
• Week number confusion: ISO weeks don't align with calendar months
• Day-of-week guessing: Never estimate—always calculate

Quick Reference

• Days in months: Jan=31, Feb=28/29, Mar=31, Apr=30, May=31, Jun=30, Jul=31, Aug=31, Sep=30, Oct=31, Nov=30, Dec=31
• 2025 Doomsday: Friday (4/4, 6/6, 8/8, 10/10, 12/12 are all Fridays)
• See references/calendar_rules.md for leap year rules, holiday calculations, and verification methods