Calculators & everyday math
Leap-Day Birthdays: How February 29 Ages Are Counted
About one day in every 1,461 is a February 29, so leap-day birthdays are rare — and they raise a real question: in a year without February 29, when does the birthday happen? This guide explains the two common answers and how age calculators handle them.
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Two conventions
- February 28: the birthday is taken as the last day of February. This is how most date software adds years and months, and it is what the Looty Tools Age Calculator uses.
- March 1: the birthday is taken as the day after February 28. Some legal systems use this date for when a person born on February 29 reaches a new age.
An example
Ages for someone born on February 29, 2000 under each convention:
| Date | Age with the February 28 rule | Age with the March 1 rule |
|---|---|---|
| February 27, 2025 | 24 | 24 |
| February 28, 2025 | 25 | 24 |
| March 1, 2025 | 25 | 25 |
| February 29, 2028 | 28 | 28 |
How often the real birthday comes around
February 29 exists in years divisible by 4, except century years not divisible by 400 — so 2000 had one, but 1900 and 2100 do not. Most leap-day babies get a real birthday every four years; someone born on February 29, 2096 would wait eight years for the next one, until 2104.
Which rule to use
For everyday purposes either works, and many people simply celebrate on whichever day they prefer. When age has legal consequences — a license, a benefit, a contract — check the rule the relevant authority uses.
Leap-Day Birthdays FAQ
- When does someone born on February 29 turn a year older?
- On February 29 in leap years. In other years it depends on the convention: February 28 or March 1.
- Which date does the Age Calculator use?
- February 28, the last day of February. It shows a note whenever the birth date is February 29.
- How old is someone born on February 29, 2000 on February 28, 2025?
- 25 under the February 28 rule, and still 24 under the March 1 rule.
- How often is there a real February 29 birthday?
- Usually every four years, but century years not divisible by 400 skip it, so the gap across 2100 is eight years.
- Does the convention change the age in days?
- No. The total number of days alive is the same either way; only the day the year count goes up differs.
Related guides
- How Age Is CalculatedHow completed years, months, and days are counted on the calendar, why dividing by 365.25 goes wrong, and how to check an age by hand.
- Leap Years and Day CountsWhich years are leap years, how February 29 changes day counts, and why 365 days after a date isn’t always the same date a year later.
Open the tool
Jump into Age Calculator when you are ready to process your files.
