Date Difference Calculator
Pick a start date and an end date to see exactly how many days, weeks and months lie between them.
| Total days | |
| Weeks | |
| Calendar months | |
| Years, months, days | |
| From | |
| To |
How to calculate the difference between two dates
The total number of days is found by counting every calendar day from the start date up to (but not including) the end date. Divide that total by 7 to get weeks: the whole-number part is full weeks and the remainder is leftover days. For example, from January 15, 2026 to October 15, 2026 there are 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 = 273 days, which is exactly 273 ÷ 7 = 39 weeks.
Months are counted on the calendar rather than as a fixed number of days, because months vary from 28 to 31 days. The calculator steps forward one calendar month at a time from the start date for as long as it does not pass the end date, then counts the days left over. In the example above, January 15 to October 15 is 9 full calendar months and 0 days. From January 31 to March 1, 2026 it is 1 month (January 31 to February 28) and 1 day.
The years, months, days breakdown simply groups every 12 of those calendar months into a year. All counting is done in UTC so daylight-saving changes never add or remove an hour and skew the day count.
Frequently asked questions
Does the calculator include the end date?
No. It counts the days from the start date up to but not including the end date, which is the standard way to measure elapsed time. If you need an inclusive count, such as the number of days a hotel stay or rental covers, add 1 to the total days.
Why do months not equal total days divided by 30?
Calendar months are different lengths, from 28 to 31 days, so the calculator counts actual calendar months from your start date rather than dividing by an average. This matches how birthdays, leases and billing cycles are normally counted.
What happens if the end date is earlier than the start date?
The calculator automatically swaps the two dates and tells you it did so, so you always get a positive difference.