HaatBeatHow it's calculated
Age = whole months from the birth date, then the remaining days
Months are counted on the calendar, so a month is not a fixed number of days. When a month is too short for the birth day (for example 31), its last day counts.
Assumptions
- Dates are calendar dates in your own time zone; the time of birth is not used.
- A 29 February birthday is counted on 1 March in years without that date.
Worked example
Someone born on 15 January 1990 is 36 years, 8 months and 15 days old on 30 September 2026.
Questions
How is a 29 February birthday handled?
In years without 29 February it is counted on 1 March, the day after 28 February. Local legal rules can differ, so check them where it matters.
Why is "today" set by my device?
The calculator uses your device’s date so it matches where you are, even across time zones.
Can I work out an age on a past or future date?
Yes. Change the "Age on" date to any date on or after the date of birth.