Add to or subtract from a date
Deadlines, notice periods, due dates — with the weekday you’ll land on.
Sunday, 23 August 2026
Years and months are applied before weeks and days. A day that doesn’t exist in the target month — 31 September — clamps to the last one that does.
- Resulting date23 November 2026
- Falls on aMonday
- ISO format2026-11-23
- Days from the start92
The end-of-month rule
One month after 31 January is 28 February — there is no 31st to land on, so the date clamps to the last day that exists. Every calendar application and spreadsheet does this, and it has a consequence worth knowing: the operation doesn’t reverse. Subtract that same month again and you get 28 January, not the 31st you started from.
Because of that, the order the parts are applied in changes the answer, so it’s fixed: years, then months, then weeks and days. One month and one day after 31 January is 1 March; one day and then one month would be 28 February.
Counting the other way
To measure the gap between two dates you already have rather than project forward from one, use the date difference calculator, which also counts business days. The two are exact inverses — adding what one reports gets you back to where the other started.
