Date calculation
Add or subtract days, weeks, months, and years from the start date.
Date Calculator
Add or subtract days, weeks, months, and years from a start date, with the calculated date and weekday shown first.
Add or subtract calendar units
Select a start date, choose Add or Subtract, and enter the day, week, month, and year amounts. The result applies calendar units rather than treating every month as a fixed number of days.
Starting on 2026-01-01 and adding 10 days gives 2026-01-11. Adding one month uses the corresponding calendar month and the calculator's visible end-of-month handling. Negative values are not a substitute for changing the Add or Subtract setting.
Date boundaries
The calculation uses calendar dates and returns a date, not elapsed hours. Time zones and daylight-saving changes do not add or remove a calendar day from this result. Use Date Duration Calculator to measure the span between two dates.