What the calculator reports
Pick a start and end date and the tool returns the total number of days, the number of whole weeks, and a calendar breakdown in years, months and days. Dates are read as calendar dates in your own time zone, so the result does not shift by a day and daylight saving changes do not matter. Total days is the number of calendar days between them. The weeks figure is the total divided by 7, rounded down, so leftover days are not shown in that box. The breakdown counts whole calendar months from the start date (dropping one if the end day-of-month has not been reached), then shows the remaining days.
Worked examples
| Start | End | Total days | Y / M / D |
|---|---|---|---|
| 2024-01-01 | 2024-12-31 | 365 (366 with end date included) | 0 / 11 / 30 (1 / 0 / 0 with end date included) |
| 2024-02-01 | 2024-03-01 | 29 (2024 is a leap year) | 0 / 1 / 0 |
| 2026-01-01 | 2026-12-25 | 358 | 0 / 11 / 24 |
The first row is a good illustration of the include-end-date option. Counting from 1 January to 31 December gives 365 days elapsed, but a project that runs on both of those dates occupies 366 calendar days. The checkbox adds that one day to the totals, and the years, months and days breakdown is measured through the end of the end date too, so the same span reads 1 year, 0 months, 0 days.
Inclusive or exclusive?
- Exclusive (default). Counts the nights or the gap between two dates. Monday to Wednesday is 2 days. Use this for ages, notice periods and "days until" questions.
- Inclusive. Counts every date on the calendar, so Monday to Wednesday is 3 days. Use this for hotel-style stays billed per day, attendance periods or sprints where both end dates are working days.
The tick box changes every figure in the same way: total days and weeks gain the extra day, and the years, months and days breakdown is calculated up to and including the end date. For example, 1 January to 31 January shows 30 days (0 months, 30 days) by default and 31 days (1 month, 0 days) with the end date included.
Limits to be aware of
- The tool counts every calendar day, with no weekend or holiday exclusion, so it will not give working days.
- If the end date is earlier than the start date, the tool swaps them and shows a note, so total days, weeks and the years/months/days breakdown all describe the span between the two dates as positive figures.
- Months are not a fixed size. 31 January to 28 February counts as 0 months 28 days in this method, while many spreadsheet functions give different answers. When a contract defines "a month", follow its wording.
For a person's age with a next-birthday countdown, use the age calculator. To convert a duration into seconds or compare epoch values, see the timestamp converter.