Date Calculator
Find the difference between dates or add and subtract calendar time.
How to use Date Calculator
Date differences are signed: an earlier end date produces a negative result. The end date is not counted inclusively.
Details and limits
Years and months are combined and applied first, clamping to the final day of the target month. Weeks and days are applied afterward. January 31 plus one month becomes February 28, or February 29 in a leap year.
Practical example
Date difference measures elapsed calendar days, not an inclusive count of both endpoints. Adding months adjusts invalid month-end dates to the last valid day.
From 2025-03-01 to 2025-03-11 is 10 days. Adding one month to 2025-01-31 gives 2025-02-28, since February has no 31st day.
Frequently asked questions
Are weekends and holidays excluded?
No. Weeks and days use calendar arithmetic, including weekends. There is no business-day calendar or holiday list.
Can adding a month and subtracting it return a different date?
Yes. Month-end clamping loses the original day: January 31 plus one month may become February 28, then minus one month gives January 28.
Why is a very distant result rejected?
The supported calendar range is years 0001 through 9999. Even valid starting dates can exceed it after a large adjustment.