Days Between Dates Calculator
Exact days, weeks and months between any two dates.
About this calculator
Notice periods, project timelines, interest calculations, "how long until…" — dozens of everyday questions reduce to the number of days between two dates. This calculator gives the exact day count plus the same gap expressed in weeks and in calendar years/months/days.
The formula
Worked example
From 1 March 2026 to 18 July 2026 is 139 days — 19 weeks and 6 days.
Common mistakes
- Counting both endpoints — the convention is to exclude the start day and include the end day.
- Using calendar days where a contract says working days (use the Business Days calculator).
- Assuming every month is 30 days in interest calculations that specify actual days.
Frequently asked questions
Assumptions & limitations
Pure calendar day counting, no time-of-day component.
Sources & verification
This calculator applies the standard formula published above to the figures you enter — it relies on no external statutory data. The formula and the worked example were checked by hand against each other.
Spotted an error or an out-of-date figure? Report it — corrections are prioritised over all other work (see our corrections policy).