Date Arithmetic
Add or subtract days, weeks, months, and years from a date
Result
Friday, July 3, 2026
ISO: 2026-07-03T00:00:00+00:00
Day of week: Friday
Day of year: 184
Week: 27
Total offset: 30.00 days · 720 hours
About Date Arithmetic
Calculate dates relative to a starting date — useful for project deadlines ("90 days from today"), birthdays, contract end dates, or any "when will it be?" question. Combine years, months, weeks, days, hours, and minutes in one calculation.
Months and years preserve the day-of-month where possible. Adding 1 month to January 31 lands on February 28/29 (the last day of the next month), since February doesn't have a 31st.
Frequently asked questions
How are months handled?
Calendar months — adding one month to January 15 gives February 15, not "30 days later". When the target month is shorter (e.g. February), the date snaps back to the last valid day.
Does it handle leap years?
Yes — calculations use the proper Gregorian calendar including all leap-year rules.