How many days does February have?

February has 28 days in a common year and 29 in a leap year. It is the only month whose length varies and the only one with fewer than 30 days. Leap years occur 97 times in every 400 years, so 28 days is the answer roughly three years in four.

What is the complete leap year rule?

A year is a leap year if it is divisible by four, except that years divisible by 100 are not, unless they are also divisible by 400. So 1900 was a common year, 2000 was a leap year, and 2100 will be a common year.

Why was the century exception added to the calendar?

Because a leap year every four years assumes a year of 365.25 days, when it is nearer 365.2422. The Julian calendar therefore gained about a day every 128 years. The Gregorian reform of 1582 dropped three leap years per 400 years to correct the drift.

When do people born on 29 February celebrate their birthday?

In common years they use either 28 February or 1 March, and both are widespread. Some legal systems specify which date counts for reaching a given age, so the answer can depend on the country as well as on personal preference.

How Many Days in February

Every other month has a settled length. The days in February depend on the year, and the rule that decides it is more involved than the familiar every-four-years version most people carry around. Two exceptions sit on top of it, one of which only bites in years ending in double zero, and getting them wrong is a classic source of quiet errors in spreadsheets and scheduling code.

This article gives the full rule, explains why February ended up as the short month in the first place, and covers what 29 February means for people born on it. For the length of any month without the history, the days in month page answers directly.

How Many Days in February?

February has 28 days in a common year and 29 in a leap year. It is the only month whose length changes, and the only one shorter than 30 days. Every other month has either 30 or 31 days, fixed.

Leap years account for 97 years in every 400, so roughly a quarter of the time the days in February run to 29. That makes 28 the answer in about three years out of four, and it is why the month is treated as the exception in every mnemonic — including the rhyme and the hand method described in the knuckle mnemonic, neither of which can express it without a special case.

The Full Leap Year Rule

Three tests, applied in order, settle whether a year has 29 days in February:

Divisible by 4: if not, it is a common year and February has 28 days. This test alone resolves most years.
Divisible by 100: if it is, the year is not a leap year after all, despite passing the first test.
Divisible by 400: if it is, it is a leap year regardless of the second test.

The worked examples make it concrete: 1900 is divisible by 4 and by 100 but not by 400, so it was a common year with 28 days in February. The year 2000 is divisible by 400, so it was a leap year. The year 2100 will be a common year for the same reason 1900 was. This century rule is the part most often omitted from software, and because the exception to the exception applies in years like 2000, badly written code can appear correct for a hundred years before failing.

Applied in that order the rule is unambiguous, and it is the only calculation needed to know the days in February for any year. Nothing else about the calendar changes: the other eleven months keep their lengths, and only the days in February move between 28 and 29.

Why Does February Have Only 28 Days?

Because it was the last month of the early Roman year and absorbed whatever days were left over. The Roman calendar began in March, so the shortfall between the named months and the solar year had to sit somewhere, and February was where the sequence ended.

The ten-month Roman year had no January or February at all; the winter gap was simply uncounted. Numa Pompilius is traditionally credited with adding Januarius and Februarius to close it. Februarius took its name from februa, the purification rites held during it, and being last, it was the month left short. The full picture of how the year was reshaped is set out in why September is the ninth month.

The popular claim that Augustus stole a day from February to make August as long as Julius Caesar's month is a later invention. It appears only in medieval writing, more than a thousand years after the fact, and the month lengths look to have been settled at the Julian reform.

Where 29 February Came From

The Julian reform of 46 BC under Julius Caesar fixed the year at 365 days and added an extra day every fourth year to absorb the remaining quarter-day. That extra day went into February, because February was already the flexible month where the old calendar had inserted its intercalations.

The Romans did not append a 29th day at the end. They doubled the sixth day before the Kalends of March, giving the leap year an extra bis sextum — a doubled sixth — which is why leap years are still called bissextile in formal and legal English. The modern practice of writing the extra day as 29 February came later, and it is the reason a leap day sits mid-month in Roman terms but at the end of the month in ours.

The Century Exception and Why It Exists

The Julian rule of one leap year in every four assumes the year is exactly 365.25 days long. It is closer to 365.2422, so the Julian calendar ran about eleven minutes long each year and drifted a full day roughly every 128 years.

By the sixteenth century the accumulated error had moved the spring equinox well away from its assumed date, which mattered because the date of Easter was calculated from it. The reform issued under Pope Gregory XIII in 1582 removed ten days from the calendar and added the century rule, which drops three leap years in every 400. That brings the average year to 365.2425 days — accurate to within about a day every three thousand years, and the basis of the Gregorian calendar still in use. Britain and its colonies did not adopt it until 1752, by which time eleven days had to be dropped, an adjustment that still echoes in the odd start date of the UK tax year, as noted in fiscal quarters explained.

Leap Day Birthdays

Around one person in 1,461 is born on 29 February, and they are sometimes called leaplings. A true birthday arrives only in leap years, so most years require a substitute date, and there is no single universal answer to which one it should be.

Practice divides along two lines, and both are common:

28 February: preferred by those who want the anniversary to fall in the same month, and used by several legal systems for determining when a person reaches a given age.
1 March: preferred by those who count a full year from the birth date, and also written into law in some jurisdictions.
Both: a common informal compromise, particularly for children.
Documents and forms: the date is valid and must be accepted, though poorly written validation still rejects it, which is the practical annoyance most leaplings actually report.

Anything scheduled annually on the 29th faces the same question, from renewals to review dates, which is usually resolved by falling back to the last day of the month — whichever of the two possible days in February that turns out to be. The days remaining in the current month, whichever month that is, are shown on this month, and the full month-by-month reference sits in how many days in each month.

Conclusion

The days in February are 28 in a common year and 29 in a leap year, decided by a rule with two exceptions: divisible by four is a leap year, unless divisible by 100, unless also divisible by 400. February is short because it ended the old Roman year and absorbed the leftover days, and it holds the leap day because that is where the Julian reform put it. The century exception exists because a quarter-day a year is slightly too much correction. To check the length of February or any other month, open the days in month page or the rest of months.now.

February and Leap Years: How Many Days in February and Why