If you were born on 29 February, the day you legally turn 18 (or any age) in a non-leap year is either 28 February or 1 March, depending on where you live. Some places write it into law: Hong Kong and Taiwan both use 1 March. Many others, including most US states, have no specific rule, and the answer depends on how their courts count a person’s age.
Here’s how the rule works, the laws that spell it out, and how to check your own age on any date.
How Rare Is a Leap Day Birthday?
29 February comes round once every four years, so it’s one day in every 1,461 (365 × 4 + 1). If births were spread evenly through the calendar, about 1 person in 1,461 would be a “leapling”. Real birth rates vary by season and by country, so treat that as a rough guide.
28 February or 1 March: Why There Are Two Answers
In a non-leap year, a leapling’s “birthday” doesn’t exist, so the law has to pick a day either side. The choice usually comes down to one technical question: does the day of birth count as a day already lived?
- If the day of birth is counted, you complete each year at the end of the day before your birthday. For a leapling that’s the end of 28 February, so you turn 18 on 28 February.
- If the day of birth is not counted, you complete the year only when the calendar reaches the equivalent date. With no 29 February, that’s 1 March.
A Thomson Reuters legal blog summarises the US position this way: if a state excludes the day of birth, a leapling turns 18 or 21 on 1 March; if it includes it, on 28 February. Some states have statutes on it; many don’t.
Places That Put It in Writing
| Jurisdiction | Legal birthday in a common year | Source |
|---|---|---|
| Hong Kong | 1 March | Law since 1990: “Where a person has been born on February 29 in a leap year, the relevant anniversary in any year other than a leap year shall be taken to be March 1.” |
| Taiwan | 1 March | Civil Code: if a period has “no corresponding day in the last month, the period ends with the ending of the last day of the last month”, so the anniversary is reached as February ends. |
| United States | Varies by state | Depends on each state’s statute or common-law rule on counting the day of birth |
Rules can change and court decisions can be narrow, so for anything that matters, such as a driving licence, a contract, a pension or an age limit for a job, check with the office that applies the rule.
What It Means in Practice
For most day-to-day purposes it makes little difference. Shops, venues and websites usually check the year, and by 1 March a leapling is past any cut-off either way. The one day in question matters mostly when something happens on 28 February itself: signing a contract, sitting an exam with an age limit, or a benefit that starts at a particular age.
Celebrating a Leap Day Birthday
Many leaplings celebrate on 28 February in common years, because it keeps the birthday in February. Others choose 1 March because it’s the day they actually complete another year. There’s no right answer for a party, and some families celebrate both.
Our free birthday countdown treats a 29 February birthday as 1 March in non-leap years, the same approach as Hong Kong and Taiwan law. For a 29 February 2004 birthday, it shows the next birthday as 1 March 2027.
How to Check Your Age on Any Date
- Open the age on a date calculator.
- Enter your date of birth, 29 February.
- Enter the date you want to check, for example 28 February and then 1 March of your 18th birthday year.
The result shows your exact age in years, months and days on each date, so you can see the difference the rule makes.
Frequently Asked Questions
When does someone born on 29 February turn 18?
In a non-leap year, on either 28 February or 1 March, depending on local law. Hong Kong and Taiwan use 1 March. In the United States it depends on the state: those that exclude the day of birth use 1 March, those that include it use 28 February.
How old is a leap year baby, really?
The same age as anyone born that year. A person born on 29 February 2004 turns 21 in 2025, even though there have been only five 29 Februarys since. Joking that they’re “only 5” counts leap days, not years.
How common are leap day birthdays?
29 February is one day in every 1,461, so if births were spread evenly, roughly 1 person in 1,461 would be born on it. Actual numbers vary because birth rates differ by season and country, and because of scheduled births.
Which date should a leapling celebrate on?
Whichever feels right. Many choose 28 February to stay in February; others prefer 1 March, when they legally complete another year in places like Hong Kong. For official purposes, follow the rule where you live.
Check your exact age on any date with the free age on a date calculator, or count down to your next birthday with the birthday countdown.
Sources: Thomson Reuters, “The leap year and the law”; Hong Kong and Taiwan provisions as quoted in Wikipedia, “Leap year”.