➕ Date Adder/Subtractor
Enter a date and how many days, weeks, months or years to add (use negative numbers to subtract) to find the resulting date.
The order the units are applied
The four boxes are not added together into one number of days. They are applied to the date one after another, and the order changes the answer at month ends:
years first then months then (weeks x 7) + daysWeeks and days are pure counting, so 8 September 2026 plus 90 days is Monday 7 December 2026 whatever else is in the form. Years and months move the calendar field instead, which is why 31 January plus one month gives 3 March 2026 rather than 28 February: there is no 31 February, so the extra three days spill into March. Negative numbers subtract, and a blank or non-numeric box counts as zero.
Leap days and the ISO row
- 29 February 2028 plus one year lands on 1 March 2029, since 2029 has no 29 February. Add 365 days instead if you want the same calendar slot.
- The headline result and the weekday are in your local time. The ISO row beneath is rendered in UTC, so east of Greenwich it can read one day earlier - trust the long-form date.
Frequently asked questions
What date is 90 days from today?
Put the number in the Days box and leave the rest at zero. From 8 September 2026 the answer is Monday 7 December 2026.
How do I subtract days from a date?
Type a negative number, such as -30 in the Days box. Boxes can be mixed, so -1 year with +14 days goes back a year then forward a fortnight.
Why did adding a month to 31 January give me 3 March?
February has no 31st, so the date overflows into the following month. That is standard date arithmetic - end-of-month dates need checking by eye.