Date Calculator
Add or subtract a number of days, weeks, months, or years from any starting date to find the resulting date — useful for deadlines, due dates, and planning.
Show solution steps
What is the Date Calculator?
A date calculator lets you move forward or backward from any starting date by a chosen number of days, weeks, months or years, without manually counting on a calendar — useful for working out deadlines, due dates, notice periods, contract end dates or event planning.
How to Calculate
Pick a start date, choose whether to add or subtract, select the unit (days, weeks, months or years) and enter the amount. The calculator applies the offset directly to the calendar, correctly handling shorter months and leap years — for example, adding one month to 31 January lands on 28 or 29 February, whichever is valid that year, rather than an invalid date.
Formula
The calculator takes your start date and applies the chosen offset, correctly handling month-length differences and leap years (e.g. adding 1 month to 31 January lands on the last valid day of February).
Worked Example
Adding 30 days to 1 January 2026 gives 31 January 2026. Subtracting 1 year from 12 July 2026 gives 12 July 2025.
How to Use
- Enter your start date.
- Choose Add or Subtract.
- Enter the amount and unit (days, weeks, months, or years).
- Read the resulting date instantly.