Counting days between dates matters for deadlines, notice periods, interest and leave. The maths is easy to get slightly wrong by hand — mostly because of one question: do you count both end dates, or just the gap between them?
Inclusive or exclusive counting
From Monday to Wednesday, is that two days or three? If you count the days that pass, it is two; if you count the days you are present (Mon, Tue, Wed), it is three. Contracts and leave policies differ, so decide which your situation needs — a good calculator can show both.
How to count
- Open the date difference calculator.
- Pick the start and end dates.
- Read the total in days, and in weeks and months where useful.
Working days vs calendar days
A 30-day calendar period is only about 22 working days once you drop weekends. For notice periods and delivery estimates that are quoted in business days, count working days instead of calendar days, and remember public holidays are not included automatically.