Leap day birthdays: how old is someone born on 29 February?

Someone born on 29 February 2000 turned 26 years, 4 months and 8 days old on 7 July 2026 — a perfectly normal age. What’s unusual is that they’ve only lived through 6 actual 29 Februaries to get there: 2004, 2008, 2012, 2016, 2020 and 2024. The calendar owes them a birthday most years and pays it back roughly once every four.

The worked case

Take that 2000 birth date as the reference point. By 7 July 2026 the person is 26 years, 4 months and 8 days old, counted the same way anyone’s age is counted: full years and months elapsed, plus the remaining days. Their date of birth has existed on the calendar only six times since they were born, in 2004, 2008, 2012, 2016, 2020 and 2024. Every other year, 29 February simply isn’t a date — the calendar moves straight from 28 February to 1 March. The person still ages normally in those years. Age is a measure of elapsed time, not a count of birthdays, so the two numbers — 26 years old, 6 real birthdays — are both correct and not in tension.

When to celebrate in ordinary years

In the three years out of four when there’s no 29 February, people born that day mark the occasion on 28 February or 1 March, and either is generally accepted as fine. It’s mostly a matter of personal or family preference. Where it stops being a preference and becomes a technical question is coming-of-age: turning 18 for a driving licence or 21 for some other legal threshold needs an actual calendar date to trigger on, and rules differ by country as to which day — the 28th or the 1st — counts as that trigger. If a specific legal deadline hinges on it, that’s worth checking against the relevant jurisdiction rather than assuming.

The rarer trap

Leap years follow a rule with an exception built into the exception. A year divisible by 4 is normally a leap year, but a year divisible by 100 is not — unless it’s also divisible by 400. That’s why 1900 had no 29 February, while 2000 did. It also means 2100 will skip the leap day entirely, even though 2096 and 2104 either side of it won’t. For most people born on 29 February, this is invisible; the next few leap years — 2028, 2032, 2036, 2040 — arrive on schedule every four years. But anyone doing long-range date arithmetic across a century boundary needs to remember that the four-year pattern isn’t absolute.

Work out any leap-day age

Because 29 February only exists on the calendar in certain years, age calculations that don’t account for it can quietly go wrong — treating the birthday as if it fell on 28 February or 1 March every year, and drifting by a day depending on the method. The date calculator handles this correctly: it counts elapsed time between two real calendar dates and doesn’t need the birthday itself to exist in every intervening year to get the answer right.