How the date calculation works
The calculator moves through the real calendar by the amount you enter. Days and weeks use calendar-day increments; months and years preserve the day number when possible and use the last valid day when the destination month is shorter.
Date calculation example
Adding one month to January 31, 2027 returns February 28, 2027 because February has no 31st day.
What to know
- Negative offsets are not needed—choose Subtract instead.
- The result is a calendar date, not a fixed number of hours.
Frequently Asked Questions
Can I subtract a date interval?
Yes. Choose Subtract, then enter a non-negative whole number and a unit.
How are leap years handled?
The calculation uses the actual calendar, including February 29 in leap years.