Add or subtract days, weeks, months and years from a date
Add or subtract days, weeks, months, years, hours or minutes from a date, and get the resulting date with its weekday and ISO week.
Runs entirely in your browser — nothing is uploaded.
Adding months clamps to the end of the month: 31 January plus one month is 28 February, not 3 March. All arithmetic is in UTC, so daylight-saving changes never shift the result.
How to use
- Choose add or subtract. Or enter a negative amount, which does the same thing.
- Pick the start date and amount. Then select the unit.
- Read the result. The resulting date, the day of the week, and the ISO week it falls in.
Questions
What happens when I add a month to 31 January?
You get 28 February — or 29 in a leap year. The result clamps to the last day of the target month rather than rolling over into March, which is what almost everyone means by "a month later".
How many days are in a month here?
Adding months uses real calendar months, not a fixed 30 days. Adding one month to 31 March gives 30 April; adding 30 days gives 30 April too, but adding one month to 31 January and adding 30 days give different answers.
Does daylight saving affect the result?
No. All arithmetic runs in UTC, so adding 30 days always advances exactly 30 calendar days even across a clock change.
Can I work out a deadline in working days?
Not with this tool — it counts calendar days. Use the business days calculator, which skips weekends and public holidays.