Date add and subtract calculator
When a period reads like 1 year, 2 months and 10 days, enter each part in its box to get the resulting date.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter start date, operation, years, months, weeks and days.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Years and months are applied first (using the last day of a shorter month), then weeks × 7 and days are added.
Example
Inputs: Start date = 2026-10-01, Operation = Add, Years = 1, Months = 2, Weeks = 3. Result: Resulting date: Sunday, December 26, 2027 (2027-12-26); Day of the week: Sunday; Difference in days: 451.
Limits and caveats
- The order matters at month ends; this tool applies years and months before days.
Questions about this tool
Why are months applied before days?
Month lengths vary, and most calculators and spreadsheets use this same order for a predictable result.
Can I leave some boxes at zero?
Yes, put 0 in any part you do not need.
What is the difference in days?
It is the real number of calendar days between the entered date and the result.