📏 Days Between Dates Calculator
Count the days between two dates and see the same gap in weeks, months, years, weekdays and hours.
How to use it
Pick a start date and an end date and the number of days between them appears instantly, along with the same span in weeks, months, years, weekdays and hours. Enter them in either order — the calculator swaps them if needed. The shortcut buttons answer common questions like "how many days are left this year?" and "what day of the year is it?".
Should you include the end date?
The most common mistake in date math is being off by one day.
- Don't include end date (difference) —
end − start. Jan 1 to Jan 2 is 1 day. Use this for "how many days ago", elapsed time, ages and countdowns. - Include start and end dates —
end − start + 1. Jan 1 to Jan 2 is 2 days. Use this for "how many days long": vacations, trips, employment periods, hospital stays, project durations.
Example: a vacation from Monday, March 2 through Friday, March 6 is a 4-day difference but a 5-day vacation.
How it's calculated
- Days Both dates are converted to midnight UTC and the difference is divided by 86,400,000 ms, so daylight saving time changes never add or lose a day.
- Months A month is counted each time the start day-of-month comes around. Jan 15 → Mar 20 is 2 months, 5 days.
- End of month If a month doesn't have that day, its last day counts. Jan 31 → Feb 28 (common year) is 1 month, 0 days; Jan 31 → Mar 31 is 2 months.
- Weekdays Monday–Friday dates in the range. Federal and public holidays are not subtracted — take out Memorial Day, July 4th, Thanksgiving and so on yourself if you need business days.
Which method to use
| Situation | Recommended |
|---|---|
| Length of employment, days worked | Include both dates |
| Trip, vacation or hospital stay length | Include both dates |
| Days since an event, countdowns | Difference |
| Interest on a deposit or loan | Check the agreement (usually difference) |
| Hotel nights | Difference (check-in to check-out) |
Legal and contractual periods have their own rules — for example, many court rules exclude the day of the triggering event and extend a deadline that lands on a weekend or holiday. When a deadline matters, follow the governing law or ask a professional.