How this calculator works
Each date is converted to a whole number of days, counted in UTC so time zones and daylight saving never shift the result. The calculator then subtracts the earlier count from the later one to get the total number of days, and works out the years, months and leftover days the same way the age calculator does: full years first, then full months since the last matching date, then the days remaining.
For example, from 1 March 2020 to 24 September 2026 is 2,398 days, which is also 6 years, 6 months and 23 days, or 78 whole months. Turning on "include the end date" adds one day, making it 2,399 days and 6 years, 6 months and 24 days.
Quick reference
| Common span | In days |
|---|---|
| 1 week | 7 days |
| 1 month (average) | ~30.4 days |
| 90 days | ~3 months |
| 1 year (common) | 365 days |
| 1 year (leap) | 366 days |
| 10 years | 3,652 or 3,653 days |
These figures are rounded averages for reference. The calculator above always works out the exact figure for the two dates you enter.
Common questions
Does the count include weekends?
Yes. The calculator counts every calendar day in the range, weekends and public holidays included. If a working-days-only figure is what you need, use the business days calculator instead.
What does "include the end date" actually change?
By default the range runs from the start date up to the end date, so 1 January to 3 January is 2 days. Turning the option on counts both dates as whole days, making the same range 3 days, useful for a hotel stay or a rental period.
Why might Excel or Google Sheets give a slightly different answer?
Spreadsheet functions like DATEDIF work out months and years by calendar position rather than by matching day-of-month, so their breakdown can differ by one unit near a month's end even when the total day count matches exactly.
How many months are between two dates?
A month is counted from a date to the same date in the following month, so 6 years, 6 months and 23 days is also 78 whole months plus the 23 leftover days.
Can I calculate the gap between dates many years apart, like 2018 to 2031?
Yes. The calculator works over any span, from a few days to many decades, and the year, month and day breakdown adjusts automatically for every leap year the range crosses.
Does this work for dates before the Gregorian calendar began?
This calculator uses the Gregorian calendar, which most of the world uses today. It was introduced in October 1582, so results for earlier dates, or for countries that adopted it later, won't match historical records from the calendar in use at the time.