A February 29 birth date is valid only in a leap year; age still advances across every later calendar date.

The elapsed calendar-day count does not disappear in a non-leap year. What can vary is the chosen observance date for a birthday label.

Worked example

A person born February 29, 2024 is one calendar day old on March 1, 2024. On February 28, 2025 the calendar span has continued normally even though February 29 is absent. This site’s next-birthday tool displays February 28 as the informational observance in a non-leap year and documents that convention in its result.

What the tool does and does not decide

The tool counts valid local calendar dates, uses the Gregorian leap-year rule, and shows a transparent next-birthday convention. It does not determine the legal birthday for a jurisdiction, the meaning of a contract, an eligibility deadline, or any official policy. Those rules can select a different date.

Common mistakes

Do not accept February 29 in 1900 or 2100. Do not add 365 days for every year. Do not assume an organization’s policy matches a consumer calculator’s display convention.

Try the next birthday calculator, read leap years and age calculations, and see the methodology for validation and limitation details.