How to use the days between dates calculator

1. Pick the start date and the end date. Both default to today and 100 days from now so you can see how it works.
2. Tick Include the end date if you want to count both ends.
3. Read the days, plus the same span in weeks, months and years.

Formula

Dates are plain calendar dates, so time zones and daylight saving time have no effect.

Worked examples

Why months are tricky

Months have 28 to 31 days, so there is no single "right" number of days in a month. The method here is calendar stepping: move forward one month at a time from the start date, using the last day of the month when the day number does not exist, and count the days left over. It matches how most people say "one month and one day."

Common uses

Count down to a deadline or event, work out how long a lease or warranty has left or check a number of days against a contract. For working days only, use the business days calculator.

Counting down to a date

Set the start to today and the end to your event. The result updates when you reopen the page because "today" is read from your device each time. For a work deadline that skips weekends and holidays, use the business days calculator.

Assumptions and limits

• The Gregorian calendar is used for all dates, including past centuries.
• Years 1000 to 9999 are supported.
• If the start is after the end, the dates are put in order and the result is positive.

Formulas reviewed October 10, 2026. See the calculation methodology for how SumPanda rounds, tests and sources its formulas.

Frequently asked questions