DocomintAdd/Subtract Days Calculator
Calculate the date N days before or after a given date.
Answers "what date is 90 days from now" or "what date was 6 weeks before this one" directly, without manually counting across month boundaries of different lengths — enter a negative number of days to subtract instead of add.
Example: 90 days after August 8, 2026 lands on Sunday, November 6, 2026 — crossing three different month lengths (August's 31, September's 30, October's 31 days) that make hand-counting error-prone.
How it works
- Enter a start date and a number of days (negative to subtract)
- Press Calculate
- The resulting date and its weekday appear instantly, computed on your device
Frequently asked questions
Can I subtract days instead of adding them?
Yes — enter a negative number in the days field (e.g. -30) to go backward from the start date instead of forward.
Does this account for daylight saving time?
Date addition here works in whole calendar days, not elapsed hours, so DST transitions don't affect the resulting date — the date 30 days later is still exactly 30 calendar days later regardless of any clock change in between.
Is my numbers uploaded anywhere?
No — Add/Subtract Days Calculator runs entirely in your browser using JavaScript/WebAssembly. Your numbers is never sent to a server.