Time Duration Formula Explained, With Examples
Every time duration 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
Duration = end − start (+24 h if end is earlier).
What each input means
- Start time: the value you enter in the calculator.
- End time: the value you enter in the calculator.
Example
For example, with these inputs:
- Start time: 09:00
- End time: 18:30
the calculator returns:
- Duration: 9 h 30 min
- In hours: 9.50 hours
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.
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.
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.
Time durations are easier to handle in minutes. Convert each time to minutes after midnight, subtract, then convert back to hours and minutes, adding 24 hours for shifts that run past midnight.
Related calculations
- Age Calculator: Calculates exact age in years, months and days.
- Days Between Dates Calculator: Counts days between two dates.
- Add Days to a Date Calculator: Finds the date a number of days after another date.
- Subtract Days from a Date Calculator: Finds the date a number of days before another date.
Use the Time Duration Calculator to plug in your own numbers.
Run your own numbers: Time Duration Calculator