Date Difference Calculator

Counting days by hand goes wrong in predictable ways: months have different lengths, February occasionally has an extra day, and it is never obvious whether the answer should include the day you started on. This does the arithmetic and shows the result several ways, because which one you want depends on why you are asking.

The years-months-days breakdown is how people describe a span in conversation. The total in days is what a deadline or a notice period needs. Working days matter for anything measured in business terms, and are counted properly rather than by dividing by seven.

The option to count both end days deserves its own mention, because it is where most disagreements come from. Monday to Friday is four days of elapsed time and five days at work. A hotel booking from the first to the fifth is four nights. Neither is wrong; they are answers to different questions, so the tool lets you pick.

Leap years are handled correctly, including the century rule that makes 1900 an ordinary year and 2000 a leap one. All the arithmetic runs in UTC, which avoids a subtler bug: subtracting local timestamps across a daylight saving change gives a period of 23 or 25 hours and can silently lose or gain a whole day.

Working days count every day that is not a Saturday or Sunday. Public holidays differ by country, state and year, so they are not deducted — subtract the ones that apply to you.