Date Calculator
Find the number of days between two dates, or the date a set number of days, weeks or months away.
1. Days between two dates
2. Add or subtract from a date
How date calculations work
- Difference vs. inclusive count differ by one day. From 1 October to 10 October is 9 days apart, or 10 days if you count the first day.
- Months follow the calendar. 15 January to 14 March is 1 month and 27 or 28 days; it only becomes 2 months on 15 March.
- Business days skip Saturdays and Sundays only. Public holidays are not removed, because they vary by country.
- Leap years are handled automatically, so 29 February is counted when it exists.
For a countdown to an event or anniversary, try the days until calculator. To work out how old someone is, use the age calculator.
Frequently asked questions
Should I include the start date?
It depends on what you are counting. The plain difference between two dates leaves out the start date (1 March to 3 March is 2 days). For things like a contract term, a course of medication or a hotel-style count where the first day counts as day one, tick "Include the start date" and the calculator adds one day (3 days).
How are business days counted?
Business days here means weekdays only: Monday to Friday. Saturdays and Sundays are skipped. Public holidays differ by country and year, so they are not removed automatically. If a holiday falls in your range, subtract it yourself.
How do you add months to a date like 31 January?
Adding months keeps the same day number in the new month. If that day does not exist, for example one month after 31 January, the calculator uses the last day of the month instead (28 or 29 February).
Does it handle leap years?
Yes. Years with a 29 February, such as 2028, have 366 days, and every calculation on this page accounts for that automatically.