Date Calculator
Add/subtract days from a date, or measure the gap between two dates.
About Date Calculator
Date Calculator does the two date-math jobs that come up daily: adding or subtracting days, weeks, months, or years from a starting date, and computing the difference between two dates in those same units. It is the practical tool for working out 'when is 90 days from today', 'how many days until a deadline', or 'how old is this in months'.
Worked example: starting from 2026-05-23, adding 90 days produces 2026-08-21. The difference between 2024-01-01 and 2026-05-23 is 2 years, 4 months, and 22 days — or 873 days total, or about 124 weeks and 5 days. Both modes update live as you change inputs, and the difference is shown in multiple units so you can pick the one the question actually needs.
Two notes worth knowing. Adding 'a month' is ambiguous, and the calculator follows the calendar-month convention: January 31 + 1 month = February 28 (or 29 in a leap year) — clamped to the end of the target month rather than rolling over into March. Day-counts default to exclusive (the strict 'days between' figure, where the start day counts but the end day doesn't); flip the 'Include end date' toggle to count both endpoints. Leap years are handled correctly because the math works on the real calendar, not a 365-day approximation.
All math runs in your browser. Personal dates — birthdays, deadlines, milestones — never leave your device.