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Date & Time Tools

Date Add and Subtract

Add or subtract years, months, weeks and days from a date to find the resulting date.

Thursday, March 25, 2027

2027-03-25

How to use it

  1. Pick a start date The date to count from.
  2. Choose add or subtract And enter the amounts to shift by.
  3. Read the new date Shown in full and as an ISO date.

Examples

Jan 31 + 1 month Feb 28/29
Jan 1 + 2w 3d Jan 18

About this tool

Working out a date a certain time before or after another sounds simple until months have different lengths and leap years get involved. This tool adds or subtracts years, months, weeks and days and gives you the exact resulting date.

Month and year shifts clamp sensibly to the end of the month, so the awkward cases behave the way you’d expect. The result is shown both as a full, readable date and as a plain ISO date you can copy. It all runs in your browser.

Frequently asked questions

How are month-ends handled?

Months and years are applied with day clamping, so adding one month to 31 January gives 28 or 29 February rather than spilling into March.

In what order are units applied?

Years and months first (with clamping), then weeks and days are added exactly, which matches how people usually think about date shifts.

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Updated June 13, 2026