Date Difference Calculator

Reviewed by the CalculatorHub team, edited by James Graham. Calculates the difference between two dates. Last verified 13 June 2026.

Finding the number of days, weeks, months, or years between two calendar dates is a surprisingly common need: calculating contract durations, determining how long until a deadline, figuring out how many days an event lasted, or checking whether a warranty or subscription period has expired. Simple subtraction fails because months and years have different lengths, and leap years create irregular day counts. The correct approach is to work from the Gregorian calendar definition directly, counting day by day from the start date to the end date (exclusive or inclusive of endpoints depending on context) to get the total calendar days, then deriving other units from that count. This calculator accepts a start date and an end date and returns the difference expressed in total calendar days, total weeks plus any remaining days, an approximate number of months based on the standard average month length of 30.4375 days, an approximate number of years, and an exact breakdown as years, months, and days calculated month by month. The exact breakdown uses the same convention as age calculations: months increment when the day-of-month in the later date reaches or passes the day-of-month in the earlier date. The default reference date is today, making it straightforward to answer the question "how many days until" or "how many days since" a given date.