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How age works for a 29 February birthday
You grow a year older every year, even when the calendar has no 29 February. Your age and the number of birthdays you have had on an actual leap day are two different things.
Someone born on 29 February 2000 is 26 by 1 March 2026. By then, they have had six later birthday anniversaries on 29 February: in 2004, 2008, 2012, 2016, 2020 and 2024. The next one is 29 February 2028, when they turn 28.
Your actual age and your leap day birthdays
| Date you check | Age reached by that date | Birthday anniversaries on 29 February |
|---|---|---|
| 29 February 2004 | 4 years | 1 |
| 29 February 2024 | 24 years | 6 |
| 1 March 2026 | 26 years | 6 |
| 29 February 2028 | 28 years | 7 |
The day you were born is the starting date, not your first anniversary. If you count it as a birthday celebration, the last column increases by one, but your age stays the same.
Dividing your age by four does not give your ordinary age. It is not always a reliable shortcut for counting leap-day anniversaries either, because some century years are not leap years.
Birthday rules for years without 29 February
In a non-leap year, a birthday calculation needs a rule for the missing 29 February. Two common choices are 28 February and 1 March.
For someone born on 29 February 2000, those choices give different completed ages on 28 February 2025:
| Birthday rule used | Birthday milestone in 2025 | Completed age on 28 February |
|---|---|---|
| Use 28 February | 28 February 2025 | 25 |
| Use 1 March | 1 March 2025 | 24 |
By 1 March, both methods give 25 completed years. The difference matters when you are checking a date close to the birthday.
You can choose when to celebrate, but that choice does not set the age rule for a license, examination, contract or benefit. For those purposes, use the rule required by the relevant authority.
Finding your next birthday on 29 February
After 29 February 2024, the next leap day is 29 February 2028, followed by 2032 and 2036. Counting down to one of those dates is different from counting down to a celebration in February or March of a non-leap year.
If you are checking on a 29 February after your birth year, that day's birthday anniversary has arrived. Once it has passed, the next birthday on an actual leap day will be in a later leap year.
Include the reference date when you save or share a result. “The next leap-day birthday is in 2028” makes sense for a calculation made in 2026. It needs updating once that birthday has passed.
Why some leap day birthdays are eight years apart
The Gregorian calendar has an exception for century years. A year divisible by 100 is a leap year only if it is also divisible by 400. So 2000 was a leap year, but 2100 will be a common year. [S02]
As a result, 29 February 2096 is followed by 29 February 2104, leaving an eight-year gap. There is no 29 February in 2100. A calculation must check the full leap-year rule instead of repeatedly adding four years.
The rule also helps you spot a possible error in a record. For example, 29 February 1900 is not a valid Gregorian date, while 29 February 2000 is valid. If a recorded date looks doubtful, check the calendar and whether it was copied correctly.
Frequently asked questions
Do leap day birthdays count as my actual age
No. That count only tells you how often a birthday anniversary has fallen on 29 February. Your age includes every year since you were born.
Which birth date should I enter on an official form
Use your recorded date of birth, 29 February. Celebrating on another day in a non-leap year does not change it.
Do I need a special rule if I was born on 28 February
No. Your birthday exists every year. Leap days may change the total days in an interval, but your birthday remains 28 February.
Can two calculators show different ages on 28 February
Yes. One may use 28 February for a leap-day birthday, while the other uses 1 March. Compare the birthday rule and the reference date in each calculation.