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The Date Add Subtract Calculator performs date math using the proleptic Gregorian calendar. Leap years follow the standard 4/100/400 divisibility rules.
Days = End Date − Start DateWhen time zones are involved, offsets are applied before differencing. Daylight saving transitions are accounted for using IANA timezone data.
Working-day calculations exclude weekends and optionally public holidays. Custom holiday lists can be applied for locale-specific schedules.
Updated: July 2026
A project manager uses the Date Add Subtract Calculator to count working days between today and a milestone, excluding weekends and holidays.
Someone calculates age, anniversary, or countdown days with the Date Add Subtract Calculator when planning an event or booking travel.
An HR coordinator verifies tenure, probation end dates, or PTO accrual periods using the Date Add Subtract Calculator for consistent date math.
Use our free Date Add Subtract Calculator for fast, accurate results in your browser. No signup or installation required — works on any device.