How to use

Days between: pick a start date and an end date. You get the number of days between them, the same span in years, months and days, in weeks and days, and the number of business days (Monday to Friday).
Add or subtract: pick a start date, enter a number, choose the unit (days, business days, months or years) and whether to add or subtract. You get the resulting date and the day of the week. The quick picks fill in common amounts, such as 30 days or 10 business days.

How it is calculated

Days between = end date − start date. For example, January 1, 2026 to December 31, 2026 is 364 days, or 365 days when both the start and end date are included.

Leap years are handled automatically, because the calculation uses real calendar dates, including February 29.

Common uses

Countdowns: days until an exam, a trip, a wedding or a deadline.
Anniversaries: how many days you have been together, or a baby’s 100th day.
Work and contracts: probation periods, notice periods, payment terms and leave.

FAQ

Does the count include the end date?

By default it counts the days in between, so March 1 to March 3 is 2 days. Tick "Include both the start and end date" when both days should count, for example for a trip or a leave request. That gives 3 days.

How do I find the 100th day?

Switch to "Add or subtract", enter the start date and 100, then tick "Count the start date as day 1". Without the tick you get the date 100 days after the start date, which is one day later.

Are public holidays excluded from business days?

No. Business days only skip Saturdays and Sundays. Public holidays differ by country and year, so subtract them yourself if needed.

How are months counted?

Months are counted forward from the start date. If the target month is shorter, the date lands on the last day of that month, so January 31 plus one month is February 28 (February 29 in a leap year). The same applies when you add months or years in "Add or subtract".