Date Difference Calculator

How this calculation works

The difference between two dates is measured in whole calendar days. Each date is treated as midnight at the start of that day, so the gap from 1 January to 2 January is exactly one day regardless of where in the world you are or whether the clocks changed in between.

The years, months and days breakdown

The headline figure counts whole months forward from the start date and then adds the leftover days. This matters at the end of a month: one month after 31 January is 28 February, because there is no 31 February, so 31 January to 1 March comes out as one month and one day. Dividing a day count by an average month length would give a different and less useful answer.

Whether the end date counts

By default the end date marks the end of the period rather than being counted as a day of its own. This is the right reading for questions like “how long until the deadline?”. Ticking Include the end date adds one day to every total, which is the right reading for questions like “how many days am I booked off?”.

Hours, minutes and seconds

These totals are the whole-day count multiplied out at 24 hours per day. Two days a year are not actually 24 hours long in places that observe daylight saving, so treat these figures as a conversion of calendar days rather than a stopwatch reading. If you need real elapsed clock time across a daylight-saving change, use the time zone converter instead.

Worked example

Limitations

• Dates are treated as calendar dates with no time of day.
• The Gregorian calendar is used throughout, including for dates before its adoption in a given country. Historical dates before the 18th century may not match contemporary records.
• Weekends and public holidays are not excluded — use the working days calculator for that.