How to calculate age
- Enter the date of birth using the date field.
- Leave the as-of date at today, or choose a past or future date.
- Select Calculate age and review the calendar breakdown and total units.
The years, months and days result is a calendar age: it accounts for the actual length of each month. Total hours, minutes and seconds are date-only conversions and do not imply a particular time of birth.
What the result includes
| Output | Meaning |
|---|---|
| Years, months and days | Calendar breakdown between the two valid dates. |
| Total months, weeks and days | Elapsed date-only totals, useful when a single unit is easier to compare. |
| Birth weekday | The weekday for the entered Gregorian birth date. |
| Next birthday | Calendar days until the next birthday under the February 29 policy described above. |
Calendar rules and limitations
- Dates are validated before calculation; impossible dates such as 31 February are not accepted.
- Leap years follow Gregorian rules, including the century-year exception.
- February 29 birthdays use February 28 in non-leap years for this page's calendar age and countdown.
- This tool does not determine legal age, biological age, school eligibility or an official identity-document date.
Age calculator questions
How does this age calculator work?
Enter a date of birth and an as-of date. The calculator subtracts the dates using Gregorian calendar rules and reports completed years, remaining months and days, plus total months, weeks, days, hours, minutes and seconds.
Can I calculate age on a past or future date?
Yes. Keep the as-of date set to today for current age, or enter any date on or after the birth date to calculate age at that point in time.
How are February 29 birthdays handled?
For a February 29 birth date, this calculator uses February 28 as the birthday in non-leap years when it calculates the calendar age and next-birthday countdown. Legal or administrative birthday rules can differ by location.
Does the calculator use the Gregorian calendar?
Yes. The calculation uses valid Gregorian calendar dates, including month lengths and leap years. Invalid dates such as February 31 are rejected.
What does total age in days mean?
Total days is the number of calendar midnights between the birth date and the as-of date. Total hours, minutes and seconds are conversions of that date-only duration using 24 hours per day; a time of birth is not entered.
Is this an official legal-age calculator?
No. It is a general chronological-age calculator for planning and reference. Age-of-majority, school, benefit and identity-document rules may use local law, cut-off times or different conventions, so confirm those requirements with the relevant authority.