Date calculator

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Count the days, weeks, months and years between two dates, or add or subtract days, weeks, months or years from a date.

How to use

Choose “Days between two dates” or “Add or subtract”.
For the difference, enter a start and end date. To add or subtract, enter a date, an amount (negative to go back) and a unit.
You’ll see the result in days, plus weeks and days and years, months and days.

Difference = end date − start date (in days)
Counting both ends = difference + 1
Adding months keeps the day of the month; if that day doesn’t exist (e.g. 31 Feb), it uses the last day of the month

1 Jan 2026 → 31 Dec 2026: 364 days (365 counting both ends) 31 Jan 2026 + 1 month → 28 Feb 2026

Should I count both the start and end date?

The main result is end minus start. For things like hotel nights or work days where both ends count, use the “counting both ends” figure.

What happens when I add a month to 31 January?

There’s no 31 February, so the result is the last day of February (28th, or 29th in a leap year).