Date Difference Calculator — Free Online Tool

The Date Difference Calculator counts the days, weeks, months, and years between two dates, and can add or subtract a number of days from a date to find another.

Counting days between dates by hand goes wrong for predictable reasons: months of differing lengths, leap years, and the question of whether both endpoints are included. That last one matters more than it seems — the gap between the 1st and the 8th is seven days if you count the interval and eight if you count the days involved. Which is correct depends entirely on what you are measuring, which is why contracts and notice periods usually specify it explicitly.

Leap years are the other reliable source of error. The rule is not simply every four years: century years are skipped unless divisible by 400, which is why 1900 was not a leap year and 2000 was. It rarely matters, and then it does.

The practical uses are mostly deadline arithmetic: notice periods, contract terms, project timelines, payment terms of 30 or 60 days, visa durations, and the gap between a purchase date and the end of a warranty. Working days rather than calendar days is a different calculation again, since it depends on which public holidays apply where.

Calculation happens instantly in your browser.

Our Date Difference Calculator is completely free to use with no signup required. For this tool, processing runs in your browser — your files and data stay on your device and are not uploaded to our servers.

Whether you are a developer, designer, student, or business owner, this tool is designed to save you time and make your workflow more efficient. Bookmark this page to access it whenever you need it — it will always be free.