What happens if I add a month to 31 January?

The result is 28 February (or 29 in a leap year). Overflowing days clamp to the last valid day of the target month, matching the behavior of the browser Date API.

Are holidays excluded from the business days count?

No. Business days counts every Monday through Friday in the range and excludes Saturdays and Sundays. Public holidays are not excluded because they vary by country and region.

Can I measure a duration where the end date is before the start date?

Yes. The calculator supports negative durations — if To is earlier than From, the values come out negative.

In what order are years, months, weeks, and days applied?

Years first, then months, then weeks (as seven days), then days. The order matters because month lengths vary, so adding 1 month and 30 days is not the same as adding 30 days and 1 month.

Date Calculator

Add or subtract days, weeks, months, and years from a date — or find the duration between two dates.

Add or subtract from a date

Start dateYYYY-MM-DD

Operation

Years

Months

Weeks

Days

Result

Saturday, July 25, 2026

2026-07-25

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Two-player chess clock with Fischer increment and Bronstein delay.

Add or subtract from a date

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