Add/subtract days, months, years from dates and calculate date differences.
Date calculations are common in project management, contract deadlines, age verification, billing cycles, and data analysis. This tool supports two operations: adding or subtracting a time period from a date, and calculating the exact difference between two dates in days, weeks, months, and years. All calculations account for varying month lengths, leap years, and daylight saving transitions.
A year is a leap year if it is divisible by 4, except for century years (divisible by 100), which must also be divisible by 400. So 2000 and 2400 are leap years, but 1900 and 2100 are not. This matters for date calculations involving February 29.
January (31), February (28 or 29 in leap year), March (31), April (30), May (31), June (30), July (31), August (31), September (30), October (31), November (30), December (31). A helpful mnemonic: knuckle months (when you make a fist) have 31 days.
This tool works with calendar dates (year, month, day) rather than exact timestamps, so timezone differences don't affect the results. For timestamp-level precision across timezones, use an epoch time converter.
This tool calculates calendar days. For business day calculations (excluding weekends and holidays), you'll need to account for your region's specific public holidays, as these vary by country and cannot be universally automated.
Adding "1 month" to January 31 gives February 28 (or 29), not March 2. Calendar month addition respects month boundaries. Adding 30 days always adds exactly 30 Γ 24 hours regardless of which months are involved.