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Date · Calculator
Add / Subtract Date
Calculate a future or past date by adding or subtracting years, months, weeks or days.
← All date calculatorsHow It Works
Years and months use calendar-aware logic. Adding 1 month to January 31 correctly returns February 28 (or 29 in leap years). Days and weeks are added as exact day offsets.
Frequently Asked Questions
What happens when I add 1 month to January 31?
It returns February 28 (or 29 in a leap year) since February doesn't have 31 days.
Can I use negative values?
Use the 'Subtract' operation instead of negative numbers. Only positive values are accepted.
Are leap years handled?
Yes. Leap years and century rules are handled automatically.
What is 'Day of Year'?
The sequential day number from January 1 (day 1) through December 31 (day 365 or 366).
Can I combine weeks and days?
Yes. Weeks are converted to days (×7) and added together.
Does this work for past dates?
Yes. Any date can be used as the base for addition or subtraction.
Last reviewed: July 20, 2026