Add or Subtract Days Calculator
Add or subtract years, months, weeks and days from a date.
About the Add or Subtract Days Calculator
Pick a start date, choose add or subtract, and enter any mix of years, months, weeks and days. The calculator gives the resulting date, its weekday, the days between and its ISO week, with a calendar view.
Years and months are added first, by the calendar, then weeks and days. If the day doesn't exist in the target month it moves to the month's last day: 31 January + 1 month = 28 or 29 February.
The formula
Result = date + years and months (calendar) + weeks × 7 + days
Worked example
90 days after 11 November 2026
- = Tuesday 9 February 2027
- 31 January 2026 + 1 month
- = Saturday 28 February 2026, as February has no 31st
Questions people ask
What's 90 days from today?
Set days to 90; deadlines in contracts are often counted this way.
Is adding 1 month the same as 30 days?
No: it lands on the same day number in the next month.
How do I count business days instead?
Use the Business Days Calculator, which skips weekends and holidays.