Add or Subtract Days
Move a date forwards or backwards by days, weeks, months, years or working days, and see which day of the week you land on. Nothing is uploaded.
| After | Date | Day |
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The gaps a notice period, a warranty or a court date usually uses, worked out from the same starting date.
How to use it
- Pick the starting date.
- Choose whether to go forwards or backwards.
- Enter the amount and the unit. Working days is the one to use for a notice period quoted in business days.
Adding months is not adding thirty days
One month after 15 March is 15 April, whether that month has 30 days or 31. The calendar decides, not arithmetic. This matters most at the end of a month: one month after 31 January is 28 February, because 31 February does not exist, so the date is pulled back to the last day that does.
A consequence worth knowing: adding one month twice is not always the same as adding two months. From 31 January, one month is 28 February and another month is 28 March, while two months straight from 31 January is 31 March. Neither is a bug. It is why contracts spell out which they mean.
Working days
The working days option steps one day at a time and counts only Monday to Friday. Ten working days from a Friday lands on the Friday a fortnight later. If the starting date is itself a weekend, counting begins at the next working day.
As everywhere else on this site, public holidays are not deducted. They differ by state, by year and by employer, and a figure that silently guessed them would be worse than one that tells you to add your own.
Why the date jumps a day on some sites
Many date tools do their arithmetic in your local time zone, and a date that crosses a daylight-saving change can come out a day short. This page works in UTC throughout, so the answer is the same in every country and on every day of the year.
Frequently asked questions
What happens when adding a month lands on a date that does not exist?
It is pulled back to the last day of that month. One month after 31 January is 28 February, or 29 February in a leap year, because 31 February does not exist. This is what contracts and banks do, and it is worth knowing that adding one month twice is not always the same as adding two months.
How does the working days option count?
It steps forward or back one day at a time and only counts Monday to Friday, so ten working days from a Friday lands two weeks later on the Friday. Public holidays are not excluded, because they differ by state and by year, so add your own on top.
Can it go backwards from a date?
Yes. Switch the dropdown from add to subtract and it counts backwards using exactly the same rules, including the month-end clamping and the working-day stepping.
Is anything I type sent anywhere?
No. The arithmetic happens in JavaScript inside your own browser. Nothing is uploaded and nothing is saved - close the tab and it is gone.