Days Between Dates Formula Explained, With Examples
Every days between dates result comes from one formula. Once you understand what goes into it, you can sanity-check any figure you are given, whether by an employer, a bank, a teacher or another website.
The formula
Days = end − start.
What each input means
- Start date: the value you enter in the calculator.
- End date: the value you enter in the calculator.
Example
For example, with these inputs:
- Start date: 1 Jan 2026
- End date: 31 Dec 2026
the calculator returns:
- Days between: 364 days
- Weeks: 52.00 weeks
- Including end date: 365 days
Why it matters
Dates and durations matter for notice periods, leave planning, project deadlines and contracts. Counting days on a calendar is slow and easy to get wrong, especially across months of different lengths.
Age is calculated in completed years, months and days. Someone born on 29 February is usually treated as turning a year older on 28 February or 1 March in non-leap years, depending on the rule being applied.
The Gregorian calendar has months of 28 to 31 days and adds a leap day almost every four years, which makes counting days by hand surprisingly error-prone. Converting dates to day numbers and subtracting avoids the problem.
Many Singapore rules are expressed in days: notice periods, leave entitlements, stamp duty deadlines and probation periods. Whether the count includes the start or end date, and whether weekends count, changes the answer.
Related calculations
- Day of the Week Calculator: Tells you which weekday any date falls on.
- Weeks Between Dates Calculator: Counts weeks between two dates.
- Months Between Dates Calculator: Counts complete calendar months between two dates.
- Time Duration Calculator: Calculates hours and minutes between two times, including overnight shifts.
Use the Days Between Dates Calculator to plug in your own numbers.
Run your own numbers: Days Between Dates Calculator