How to use
- Pick the start date and the end date. The start date begins as today.
- Choose whether to include the end date.
- Read the total in days, then the same gap in weeks, months and years.
Formula: how the days are counted
days = end date − start date
include the end date: days + 1
- Each date becomes a day number, and the two numbers are subtracted.
- Every leap day counts. Leap years are divisible by 4, except century years not divisible by 400, so 1900 was not a leap year and 2000 was.
- Weeks are the days divided by 7. Months are whole calendar months, then the days left over.
The calculator uses calendar dates, not clock times, so time zones and daylight saving can’t change the result.
Example
1 January 2026 to 31 December 2026:
- Standard count: 364 days, which is exactly 52 weeks, or 11 months and 30 days.
- Including the end date: 365 days, or exactly 1 year.
11 January to 2 May 2024 is 112 days (3 months and 21 days). The leap day, 29 February, is included.
When to include the end date
- Leave it off for elapsed time: ages, notice periods, “how long ago”.
- Include it when both days count, such as a holiday from Monday to Friday (5 days, not 4).
Common spans
| From | To | Days | With end date |
|---|---|---|---|
| 1 Jan 2026 | 31 Dec 2026 | 364 | 365 |
| 1 Jan 2024 | 31 Dec 2024 | 365 | 366 |
| 1 Feb 2026 | 28 Feb 2026 | 27 | 28 |
| 1 Feb 2024 | 29 Feb 2024 | 28 | 29 |
| 21 Oct 2026 | 25 Dec 2026 | 65 | 66 |
Month ends and hours
A month counts as complete when the same day number comes round again. A start day that a month doesn’t have moves to that month’s last day.
So 31 December 2025 to 30 April 2026 is 3 months and 30 days here. Some tools call it 4 months because April has no 31st. The total of 120 days is the same either way.
Hours are days × 24. They ignore the 23- or 25-hour days when clocks change.
Need working days only? The business days calculator skips weekends and holidays. For an exact age, use the age calculator.