Can I subtract days instead of adding them?

Yes — switch the operation toggle to "Subtract" to move backward from your start date.

Does it handle month and year boundaries correctly?

Yes. The calculator uses full calendar-date arithmetic, so it correctly rolls over month lengths, year boundaries, and leap years.

What day of the week will the resulting date fall on?

The result includes the day of the week for the calculated date automatically.

Age, Date & Calendar

Date Calculator

Pick a starting date, choose whether to add or subtract, and enter a number of days to find the resulting date.

Your calculation is performed in your browser.

Enter a start date and number of days to calculate the result.

How it works

The calculator takes your starting date and moves forward or backward by the exact number of days you enter, correctly rolling over month and year boundaries and accounting for leap years.

Formula & methodology

Result date = start date ± number of days, computed using whole-day calendar arithmetic (never by approximating months as 30 days).

Worked example

Starting from January 20, 2027 and adding 45 days gives March 6, 2027, a Saturday.

Important notes

—The number of days must be a whole number of 0 or more; choose "Subtract" to go backward in time.