How to use Add or Subtract Dates

Enter the Start date.
Fill in Years to add, Months to add, Weeks to add or Days to add. A negative number subtracts.
Choose the rule under When the target month is shorter: use the last day of that month, or stop and report that the date does not exist.
The result and the shift that was applied update as you change the fields.

Example: Add or Subtract Dates

Shift 31 January 2025 forward by one month with the clamp rule.

You add

Start date: 2025-01-31; Years to add: 0; Months to add: 1; Weeks to add: 0; Days to add: 0; When the target month is shorter: Use the last day of that month.

You get

2025-02-28, and the summary reads '2025-01-31 shifted by 1 month is 2025-02-28'. The tool notes that the date was clamped to the last day of February because 31 January is later in the month. The table also reports a difference of 28 days, counted from the start date to the shifted date.

Options

When the target month is shorter: Clamping keeps the day of the month where it exists and moves to the last day where it does not. The other option stops and names the date that does not exist.
Years to add and Months to add: Both apply together, before any weeks or days are counted. Enter a negative number to move the date backward.
Weeks to add and Days to add: These are exact calendar days. One week is seven days, and weekends and holidays are not skipped.

Supported inputs and limits

Dates run from 0001-01-01 to 9999-12-31. Each field takes a whole number: up to 10,000 years, 120,000 months, 52,000 weeks or 365,000 days, in either direction. Years and months apply first, then weeks and days, and a result outside the supported years is refused. Weekends and public holidays are not removed, so a five-day shift that starts on a Friday ends on the following Wednesday.

Where your input is processed

This tool processes your input in this browser. Your text and files are not uploaded to UseFreeTools. Check this tool's limits for anything it may save on your device.

Why the same shift length gives different spans of days

A calendar month is not a fixed number of days. Adding one month to 31 January lands on 28 February in 2025 and 29 February in 2024, so one instruction produces a 28-day move in one year and a 29-day move in the next. The result shows the date after years and months, then the weeks and days added on top.

Questions about Add or Subtract Dates

What happens when I add one month to 31 January?

February has no 31st, so the clamp rule lands on 28 February in a common year and 29 February in a leap year. Choose the stopping rule if you would rather see an error than a changed day.

In what order are the four shift fields applied?

Years and months are applied together first, then weeks and days. 2026-11-30 plus 3 months and 14 days is 2027-03-14, because the month step clamps to 28 February before the 14 days are added.

Does the tool count business days?

No. Every week is seven days and every day is one calendar day. Use the business day calculator when weekends and holidays should be skipped.

Can I subtract instead of add?

Yes. Enter a negative number in any field. Minus 3 months moves the date back three calendar months and follows the same end-of-month rule.

Project manager: Tony Hines · Content updated 29 September 2026 · Report a problem

Add or Subtract Dates

Shift the date controls