Date Calculator
Count the days between two dates, or add and subtract days, weeks, months or years.
Calendar arithmetic ยท By Stuart Mathieson · Updated October 2026
Results
Days
Weeks
Years, Months and Days
Weekdays (Mon-Fri)
Result
Weekday counts don't remove public holidays, which differ by country and region.
How the date calculator works
Days between two dates
The calculator counts from the start date up to, but not including, the end date - the same way Monday to Friday is 4 days later. Tick "include the end date" to count both days, for example for the length of a booking or an event.
It also shows the same span in weeks, in calendar years, months and days, and as weekdays. Weekdays are Monday to Friday; public holidays aren't removed, because they differ by country and region.
Adding and subtracting
Days and weeks are added on the calendar. Months and years keep the same day of the month - March 15 plus 1 month is April 15. If that day doesn't exist in the new month, the result is the month's last day, so January 31 plus 1 month is February 28 (or 29 in a leap year). Weekdays skip Saturdays and Sundays.
Worked examples
- January 1, 2026 to December 25, 2026 is 358 days - 51 weeks and 1 day, or 11 months and 24 days - and includes 256 weekdays.
- 90 days after October 23, 2026 is Thursday, January 21, 2027.
- 10 weekdays after Friday, October 23, 2026 is Friday, November 6, 2026.
- January 31, 2026 plus 1 month is Saturday, February 28, 2026.
Useful date facts
| Period | Days |
|---|---|
| 1 week | 7 |
| 4 weeks | 28 |
| 1 month | 28 to 31 |
| 3 months (a quarter) | 89 to 92 |
| 1 year | 365 (366 in a leap year) |
- Leap years are years divisible by 4, except century years, which must be divisible by 400 - so 2000 was a leap year and 2100 won't be.
- Time zones don't matter here. The calculator works with calendar dates on your device rather than times, so daylight saving changes don't affect the count.
- Counting a birthday? The Age Calculator gives an exact age in years, months and days.
Frequently asked questions
How many days are there between two dates?
Subtract the earlier date from the later one, counting the start date but not the end date. From January 1 to December 25, 2026 is 358 days, or 359 if you count both days.
Does the count include the start and end dates?
By default it includes the start date but not the end date, so the result is the number of days that pass. Tick "Include the end date in the count" to count both.
How are business days counted?
Monday to Friday are counted and weekends are skipped. Public holidays aren't removed because they vary by country and region, so subtract any that apply to you.
What is January 31 plus one month?
February 28, or February 29 in a leap year. When the same day doesn't exist in the new month, the calculator uses the last day of that month.