Add or Subtract Days From a Date

How does this calculator work?

Select a starting date, choose add or subtract, then enter the calendar years, months, weeks and days. Years and months are applied before weeks and days. If a target month has fewer days than the starting date, its last valid day is used.

Quick example

Adding one month to January 31, 2026 gives February 28, 2026, not March 3.

Frequently asked questions

Does one month mean 30 days?

No. It means one calendar month, preserving the day when possible and otherwise choosing the last day of the month.

Can I subtract time?

Yes. Choose Subtract and enter the same calendar intervals.