Quick answer
Elapsed age is unaffected. What varies is which date counts as the anniversary in non-leap years, and that answer comes from the governing rule.
How often the date actually recurs
Every four years, with one systematic exception. Century years are leap years only when divisible by 400, so 1900 was not and 2100 will not be. Anyone born on 29 February 2096 waits eight years, until 2104, for their next real birthday.
For everyone alive now the four-year rhythm holds without exception, because 2000 was a leap year. The next disruption is 2100, which affects people born on 29 February 2096 and nobody else.
Use this guide with the right tool: Open the Leap-Day Birthday Timeline for upcoming February 29 birthdays and non-leap-year anniversary context. If the question shifts, compare it with the Leap Year Calculator or the Birthday Countdown Calculator.
The legal question
Whether a leapling attains an age on 28 February or 1 March in a non-leap year is set by law, and jurisdictions genuinely differ. Some treat the anniversary as the last day of February; others treat it as the first day of March, on the reasoning that a full year is complete only once the whole of February has passed.
The answer can also depend on what the rule governs — driving, drinking, majority, contract capacity and benefit entitlement are separate rules and are not required to agree. If a threshold matters, find the specific provision rather than applying a general convention.
What is unaffected
Elapsed age, in days or in years-months-days, needs no special handling at all. Calendar-aware arithmetic counts the interval correctly whether or not the birth date is a leap day, because it is counting real dates rather than applying a rule about anniversaries.
So a leapling's exact age is exactly as computable as anyone else's. The only place the question arises is the anniversary convention, which is a labelling decision layered on top.
Practical friction
Systems that reject 29 February as invalid are still common enough to be a real nuisance, and the usual workaround — entering 28 February or 1 March — propagates into records that then disagree with the birth certificate.
If that has happened, it is worth correcting rather than living with, because the mismatch tends to surface at the least convenient moment: an identity check, a booking, a benefit application. Keep the documented date and fix the systems that will not accept it.
Worked example
Substitute your own dates and follow the instructions that actually govern your situation. Where a result sits close to a cutoff, verify the underlying date and rule independently before relying on it.
Common mistakes to avoid
- Assuming one anniversary rule applies everywhere. 28 February and 1 March are both used, and the answer can vary by what the rule governs.
- Recording a workaround date as the date of birth. It will eventually disagree with the birth certificate. Fix the system, not the record.
- Using the divisible-by-four rule for the gap. Century years break it. 1900 was not a leap year; 2100 will not be.
Use the right calculator
Each of these runs in the browser, states its assumptions, and links to the neighbouring calculation when the question turns out to be a different one.
Frequently asked questions
How many people have leap-day birthdays?
Roughly one in 1,461, which is a few million people worldwide — common enough that systems rejecting the date is a genuine problem.
When does a leapling legally turn 18?
It depends on jurisdiction and sometimes on the specific rule. Find the provision that applies rather than assuming.
Is the eight-year gap real?
Yes, around century years that are not divisible by 400. The next is 2100, affecting people born on 29 February 2096.