Leap Year Age Calculation: How February 29 Birthdays Work

People born on February 29 — "leaplings" — have a birthday only once every four years. Calculating their age in non-leap years requires a consistent convention.

In non-leap years: Most legal systems treat March 1 as the birthday for administrative purposes. A person born on February 29, 2000, would celebrate their birthday on March 1 in 2025 (a non-leap year) and on February 29 in 2024 and 2028 (leap years).

Common convention: Tooler's Age Calculator follows the March 1 convention for non-leap years. On February 28, 2025, a leapling born in 2000 is calculated as 24 years old. On March 1, 2025, they turn 25. This aligns with how most legal jurisdictions and age-verification systems handle February 29 birthdays.

Alternative conventions: Some countries use February 28 as the birthday in non-leap years. Others use March 1. The difference is rarely legally significant, as both are within one day of each other. When age verification is critical (driver's license, voting, alcohol purchase), the specific date used matters less than the consistent application of whichever convention the jurisdiction has adopted.

Why it matters: Age calculation errors for leaplings can cause issues with automated ID verification, insurance eligibility, and school enrollment cutoffs. Always verify that systems handling date-of-birth data correctly account for February 29 in both leap and non-leap years.