How to calculate chronological age
Completed years increase when the birthday anniversary has been reached. The extra months and days are based on calendar arithmetic, not an assumption that all months contain 30 days.
For example, someone born on 15 May 1990 turns 36 on 15 May 2026. For 29 February births, this calculator uses 1 March as the birthday anniversary in non-leap years. It does not estimate biological age, pension eligibility or legal age where special rules apply.
Frequently asked questions
Is my date of birth stored or uploaded?
No. The date is used locally within the browser for this calculation.
How are leap-day birthdays treated?
In non-leap years, 1 March is used by convention. Legal definitions can differ.