Date Add / Subtract
Add or subtract any number of days, weeks, months or years from a date.
Quick answer: Date Add / Subtract: add or subtract any number of days, weeks, months or years from a date. Runs entirely in your browser, free, no signup.
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Date arithmetic is deceptively tricky because the calendar is not a tidy number line, and the messiness lives in months. Adding one month to January 31 cannot land on a February 31 that does not exist, so this tool clamps to the last valid day — February 28, or 29 in a leap year. That behavior is what you want for things like "due one month after invoice date," and it is applied consistently.
Subtracting is just adding a negative number in any field, so a single input covers both directions — deadlines forward, anniversaries backward. Leap years are handled automatically, so February 29 is treated correctly whenever it genuinely occurs. Mixing units (say, add 2 weeks and subtract 3 days in one pass) is fine.
This tool answers "what date is N units from here." When your question is instead "how many days lie between two dates," that is a different calculation — reach for the Date Difference Calculator. And if weekends and public holidays should be excluded from that span, the Working Days Calculator is purpose-built for it.
Frequently asked questions
- Is the date calculator free?
- Yes — free with no signup.
- How are months handled?
- We use calendar months — adding 1 month to Jan 31 lands on Feb 28/29.
- Are my dates uploaded?
- No — every calculation runs in your browser.
- Can I subtract?
- Yes — use negative numbers in any field.
- What about leap years?
- Handled automatically — Feb 29 is treated correctly when present.