Leap-day guide
Born on February 29
Calculate the current age of someone born on leap day and understand what changes—and what does not—in years without February 29.
Why February 29 exists
Earth's orbit does not fit into exactly 365 days. The Gregorian calendar adds a leap day to keep calendar seasons aligned over time. A year is a leap year when divisible by four, except century years must also be divisible by 400.
How a leap-day age is calculated
A person born on February 29 ages continuously like everyone else. Exact age is the elapsed calendar time from the real birth date. In a leap year, a calendar birthday can fall on February 29; in other years, that date is absent.
AgeExactly uses February 28 as its practical countdown convention in a non-leap year. That convention is clearly labeled and does not claim to determine a legal birthday.
Mathematical age and legal age are different questions
Laws and administrative rules can specify whether a February 29 birthday is treated on February 28, March 1, or by another rule for a particular purpose. Those rules vary by country and context. For contracts, eligibility, licensing, or other legal decisions, consult the relevant authority rather than relying only on an online calculator.
Examples
The year 2000 included February 29 because it is divisible by 400. The year 1900 did not, despite being divisible by four, because it is a century year not divisible by 400. You can verify any full birth date with the Age Calculator.
Helpful answers
Frequently asked questions
Do people born on February 29 age only every four years?
No. Age measures elapsed time, so a person gets one year older after each full year. February 29 is simply the calendar date printed as their birthday.
When do leap-day birthdays celebrate in a non-leap year?
Many people choose February 28 or March 1. Personal custom and legal treatment are separate questions, and legal rules vary by jurisdiction.
How often does February 29 occur?
Usually every four years. Century years are not leap years unless divisible by 400, which is why 2000 was a leap year but 1900 was not.
Is February 29 valid in every year divisible by four?
Almost. The Gregorian rule excludes years divisible by 100 unless they are also divisible by 400.