How it works
Adds or subtracts a whole number of calendar days from a start date — a straightforward 24-hour-per-day count, unaffected by month length.
Add or Subtract Days
Add or subtract days (all days or business days only) from a date.
Interactive calculator
This calculator becomes interactive when JavaScript is available. The page still provides its method, limits and related tools without JavaScript.
Result classification
Mathematically exact. The result uses deterministic calendar or arithmetic rules on the values you enter. Dates are normalized before calculation, and invalid inputs are rejected.
Limitations
Exact for the stated rule and valid inputs; it does not decide legal, medical, contractual or policy questions.
Frequently asked questions
Does this handle daylight saving time?
This tool works in whole calendar days, so DST doesn't change the answer. For clock-time math across a DST change, use Add or Subtract Time.
Practical guide
Reviewed 27 July 2026How to use the Add or Subtract Days
- Enter the known values.Use the date, time, place or duration requested above.
- Check the assumptions.Confirm time zone, weekend, inclusion and rounding choices when shown.
- Read and reuse the result.Copy, share or continue to a related tool without retyping unnecessary information.
Common uses
The Add or Subtract Days is useful for project schedules, contracts, delivery dates and personal planning.
Edge cases to check
Pay particular attention to month ends, leap years, inclusive counting and dates entered in reverse order.