Days Between Dates Calculator

Both dates are read as UTC midnight, subtracted, and divided by the number of milliseconds in a day. Working in UTC matters: a local subtraction across a daylight saving change is an hour short and rounds to the wrong day. Counting both days adds one, which is why a Monday-to-Friday week is 4 days apart but 5 days long.

Should I count both the first and last day?

It depends what you are counting. A 30-day notice period usually counts both. A gap between two events usually counts neither end twice. The dropdown above switches between the two, and the difference is always exactly one day.

Does this include leap years?

Yes. The dates are subtracted directly, so February 29 is counted wherever it falls. That is why a year is sometimes 365 days and sometimes 366.

How many days are in a year?

365, or 366 in a leap year. A year is a leap year if it divides by 4, except century years, which must divide by 400. So 2000 was a leap year and 1900 was not.

Why does the weekday count not match my company holiday calendar?

Because public holidays are not subtracted here. Use the business days calculator, which lets you take holidays off the total.