Date Calculator
Days between two dates, or add and subtract time from one.
Pick a start and an end date to compare them.
How it works
Differences are counted in whole calendar days, so the same pair of dates always gives the same answer regardless of clocks or daylight saving. Adding days or weeks is fixed-length arithmetic; adding months or years is calendar arithmetic and clamps overflow — 31 January plus one month is 28 (or 29) February, never 3 March.
Example
9 August 2026 + 45 days = Friday, 25 September 2026. Between 1 January and 1 March 2024 there are 60 days, because 2024 is a leap year.
About this calculator
Two date jobs, one tool. Difference mode counts the time between two dates — total days, weeks, a calendar breakdown, and how many of those days are weekdays, which is what deadlines usually care about. Add/subtract mode moves a date forwards or backwards by days, weeks, months or years: '90 days from today' or 'three months before the deadline'.
All the arithmetic follows the real calendar — 30- and 31-day months, February, and leap years included — rather than assuming every month has 30 days.
Frequently asked questions
How do I count the days between two dates?
Pick difference mode, enter the start and end dates, and read off the total days along with weeks and a calendar breakdown. The weekday count sits alongside it, since 'ten working days' and 'ten days' are rarely the same thing.
What happens when I add a month to 31 January?
There is no 31 February, so the result clamps to the last real day of the month — 28 February (29 in a leap year). That's the standard calendar-arithmetic rule and it keeps every result a date that actually exists.
Are leap years handled?
Yes — every calculation runs on the real calendar, so February has 29 days in leap years and date differences across them come out exact.