Age: 5 Mistakes to Avoid
Calculates exact age in years, months and days. The maths is not complicated, but a handful of errors come up again and again in this and related date & time calculations. Here is what to watch for.
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.
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.
1. Mixing date formats
5/10 can mean 5 October or 10 May depending on the convention.
2. Not deciding whether to include the end date
Counting inclusively adds one day.
3. Subtracting times in decimal
9:45 minus 8:30 is 1 h 15 min, not 1.15 hours.
4. Forgetting public holidays
Working-day counts usually need holidays removed.
5. Overnight time errors
If a shift ends after midnight, add 24 hours before subtracting.
The correct method
Count whole years, then months, then days.
For example, with these inputs:
- Date of birth: 9 Aug 1990
- Age on this date: 5 Oct 2026
the calculator returns:
- Exact age: 36 years, 1 months, 26 days
- Total days: 13,206 days
- Total months: 433 months
Related calculations
- Hours Worked Calculator: Totals a shift's paid hours after breaks.
- 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.
The Age Calculator applies the formula consistently, so it is a quick way to double-check your own working.
Run your own numbers: Age Calculator