Days Between Dates Calculator

The calculator parses both dates as midnight UTC and subtracts. The difference in milliseconds is divided by 86,400,000 (the number of milliseconds in a day) to get the day count. Doing this in UTC sidesteps daylight-saving boundaries that would otherwise add a spurious 23- or 25-hour day.

Exclusive of the start, inclusive of the end. January 1 to January 2 returns 1 day — you start on the 1st, end on the 2nd, one day has passed. For "inclusive on both ends" counts (e.g. the number of *days off* on a vacation that spans Jan 1 and Jan 2), add 1.

Yes — automatically. The math is just the time difference in milliseconds, so February 29 is just another day. A year that includes a leap day returns 366 days; a regular year returns 365.

If the end is earlier than the start the result is negative — e.g. January 10 to January 1 returns −9 days. Useful for "how many days ago" calculations: pick the past date as the start, today as the end, and you get a positive day count.

This one is calendar days only. For a clock-time duration (e.g. 9:00 to 17:30) use the time-duration calculator. We'll add a business-days (workdays-only) calculator in a future version — that one needs region-specific holiday handling.