Leap Year Birthdays Explained
About five million people worldwide were born on 29 February. Their age is not unusual — but the day their birthday falls on, and the law that governs it, sometimes is.
People born on 29 February are called leaplings, or leap-year babies. They age at exactly the same rate as everyone else — the confusion is entirely about which calendar day counts as their anniversary in the three years out of four when 29 February does not exist.
The odds of a 29 February birth
There are 97 leap days in every 400-year Gregorian cycle, which contains 146,097 days. That makes the share of days that are 29 February about 1 in 1,506, or roughly 0.068 per cent of the calendar.
Actual births are slightly rarer than that, for a reason that has nothing to do with the calendar: elective inductions and scheduled caesareans are unevenly distributed across the week and the year, and a date that exists only once every four years attracts fewer planned deliveries. Estimates put the global leapling population at roughly five million.
How old is a leapling really?
Exactly as old as anyone born a day earlier or later. The joke that a leapling born in 2000 is "six years old" in 2026 is a joke about birthday parties, not about age. Age is elapsed time since birth, and time does not pause in common years.
Every age calculation for a leapling therefore proceeds normally: count the years, then the months, then the days. The only question is where the anniversary lands.
28 February or 1 March?
Both conventions exist, and which applies to you depends on where you are and what the age is for.
28 February is the more common social and administrative choice. It preserves the position of the birthday within February, which is what most people intuitively want, and it means a leapling's age increases on the last day of the same month in every year.
1 March is used in some legal frameworks. The reasoning is that a full year has not elapsed until the whole of February has passed, so the anniversary falls on the first day the year is genuinely complete. England and Wales, for example, have historically treated 1 March as the date a leapling attains an age for statutory purposes.
Our calculators use 28 February as the observed birthday, since it matches what most people expect. If you are working out a date that carries legal weight — the day someone reaches the age of majority, an eligibility cut-off, a limitation period — check the rule that applies in your jurisdiction rather than relying on any calculator, including ours.
When the gap is eight years
Leap years are usually four years apart, so most leaplings see their true birthday every four years. The exception is a century year that is not divisible by 400.
1896 was a leap year. 1900 was not. 1904 was. A leapling alive in that period waited eight years between their 1896 and 1904 birthdays. The same will happen around 2100: after 29 February 2096, the next 29 February is in 2104.
Anyone born on 29 February 2096 will have their first true birthday at the age of eight. Anyone born in 2000 got lucky — 2000 was divisible by 400 and so was a leap year, unlike 1900.
Practical advice for leaplings
- Online forms. Some booking and registration systems still reject 29 February outright, or silently store it as 28 February or 1 March. If a system will not accept the date, enter the one your official documents use and note the discrepancy somewhere you will find it again.
- Documents. Keep your passport, driving licence and medical records consistent with each other. A mismatch of one day between documents is a routine source of delay at borders and in identity checks.
- Milestone birthdays. Because true birthdays are scarce, many leaplings mark day-count milestones instead. Ten thousand days lands a little before the 28th birthday, and one billion seconds arrives at about 31 years and eight months.
- Age thresholds. For anything with a legal cut-off, work from the rule rather than the party. If your jurisdiction uses 1 March, you are not yet eighteen on 28 February.
To see the difference for a specific date, put a 29 February birth date into the age calculator. It will show the observed birthday it is using, and you can set the comparison date to either 28 February or 1 March to see both figures side by side.
Frequently asked questions
How old is someone born on 29 February?
Exactly as old as anyone born a day either side. They age at the normal rate; only the calendar day of the anniversary is unusual.
When do leaplings celebrate in non-leap years?
Most celebrate on 28 February, which keeps the birthday in the same month. Some prefer 1 March. Legal frameworks vary, and England and Wales have historically used 1 March for attaining an age.
How rare is a 29 February birthday?
About 1 in 1,506 by calendar share, and slightly rarer in practice because fewer deliveries are scheduled on the date. Roughly five million people worldwide have one.
Can the gap between leap years be more than four years?
Yes. Century years are leap years only if divisible by 400, so there was no 29 February in 1900 and there will be none in 2100. The gap either side of those years is eight years.
When does a leapling legally turn 18?
It depends on the jurisdiction. Some treat 28 February as the anniversary, others 1 March. Check the rule where you live, as it can shift the date by one day.