When's the next leap year?
The next leap year is 2028, so the next February 29 lands on Tuesday, February 29, 2028. The previous one was Thursday, Feb 29, 2024.
After 2028, leap years arrive in 2032, 2036, 2040, 2044 and 2048. The "Check a year" tab above answers for any year between 1582 and 9999.
What's the leap-year rule?
A year is a leap year under the Gregorian calendar if it's divisible by 4 — with one exception: century years (divisible by 100) are leap years only if also divisible by 400. So 1900 was skipped, 2000 wasn't, and 2100 will be skipped again. The U.S. Naval Observatory states this as the authoritative form of the rule.
In practice, four years out of every four-year block are "almost always" leap years — except at century boundaries, where three of every four centuries skip their leap day. That's why the long-run leap-year count is 97 per 400-year cycle, not 100.
The pattern is easy to read off the strip: filled circles are leap years (1600, 2000, 2400), hollow rings are the century skips (1700, 1800, 1900, 2100, 2200, 2300). 2000 looked like a routine leap year to anyone alive at the time, but it was actually the rare div-by-400 case — the first century leap year since 1600.
Why do we have leap years?
Earth's tropical year — one complete cycle of seasons — is about 365.2422 days, or roughly 365 days, 5 hours, 48 minutes, and 45 seconds. The National Institute of Standards and Technology publishes this figure (and the more precise 365.24219). A 365-day calendar would drift behind the seasons by almost a quarter of a day each year — about a full day every four years.
Adding a February 29 every four years would overshoot slightly, so the rule corrects with the century skip: 365.2425 days on average (97 leap years per 400). That's why the Gregorian calendar tracks the seasons within a fraction of a day per millennium — close enough that most people never notice the calendar moving at all.
The earlier Julian calendar (in use until 1582 in most of Catholic Europe, and well into the 20th century elsewhere) had a leap day every four years with no century exception, so it drifted about three days every 400 years. By the time the switch happened, the Julian calendar was ten days out of step with the seasons — which is why October 1582 skipped from the 4th straight to the 15th.
How rare is a February 29 birthday?
About 1 in 1,461. That's three years of 365 days plus one year of 366: 3 × 365 + 366 = 1,461 days in any four-year cycle, exactly one of which is Feb 29 — roughly 0.068%. Four times rarer than any other birthday.
Estimates put the worldwide leapling count at about five million people, ~0.06% of humans — close to but slightly below the theoretical 1-in-1,461 share, partly for a small behavioural reason: scheduled deliveries (inductions and planned cesareans) avoid the date when possible. The Birthday Rarity Calculator records the observed U.S. share as 0.0613% — a bit under the theoretical figure.
In common years, leaplings mark their birthday on February 28 or March 1; which counts as the legal birthday varies by jurisdiction. The exact-age computation for any leapling date of birth is in the Age Calculator, which handles both conventions.
A note on folklore
Two traditions cluster around the leap day: the centuries-old custom that women may propose to men on February 29 (Bachelor's Day or Sadie Hawkins Day, Irish/Scottish in origin), and Rare Disease Day, observed on February 29 in leap years and February 28 in common ones. These are framed as tradition, not data.