Subtract days from a date

Working backwards is where date math usually breaks — month lengths and leap days pile up fast. Enter a date, subtract days, weeks, months or years, and get the exact earlier date with its weekday.

Worked example

Counting backwards from Friday, 25 December 2026:

Common uses: a 90-day look-back window ending today, the start of a 30-day trial that ends on a known date, filing deadlines counted back from a hearing, and expiry checks ("was this more than 180 days ago?"). For that last one, subtract the limit from today — if the date in question is earlier than the result, it is outside the window.

Questions, answered

Is subtracting the same as adding a negative number?

Yes, exactly. This page and the add-days page use the same calendar math in opposite directions, and both agree with a spreadsheet's date arithmetic.

What date was 90 days before a leap day?

Leap days are ordinary days in the count. 29 February 2024 minus 90 days is 1 December 2023 — the counter steps through 29 February like any other date, which is precisely the step people get wrong counting by hand.