Why Does February Have 28 Days?

February has 28 days because of a Roman superstition about even numbers. When the second king of Rome, Numa Pompilius, reformed the calendar (by tradition around 713 BC), he wanted every month to have an odd number of days, since even numbers were considered unlucky. Twelve odd numbers always add up to an even total, so to reach an odd-numbered year of 355 days one month had to be even. February, a month of purification rites and offerings to the dead, got 28 days. Every later reform kept it short.

For the full history of the month lengths, see the Roman calendar article.

The ten-month calendar

The earliest Roman calendar, traditionally credited to Romulus, had ten months and 304 days. It started in March and ended in December, which is why September, October, November and December are named after the Latin numbers seven to ten. The roughly 61 days of winter after December were not assigned to any month at all. Farming did not need them counted.

Numa adds January and February

Numa's reform added two months, Ianuarius and Februarius, to bring the year closer to twelve lunar cycles. The result had 355 days:

• March, May, July (then Quintilis) and October had 31 days.
• January, April, June, August (then Sextilis), September, November and December had 29 days.
• February had 28.

February sat at the end of the year at that point. Its name comes from februa, the purification rituals held during the month, and it also contained the Parentalia festival for honoring dead family members. A short, unlucky month was a fitting place for that season.

Patching a 355-day year

A 355-day year falls about ten days behind the seasons every year. Roman priests corrected the drift by inserting an extra month, called Mercedonius or Intercalaris, in some years. They cut February short after the 23rd or 24th and slotted the extra month in, adding 22 or 23 days to that year. The decision was political, so the priests sometimes lengthened years when their allies held office and skipped insertions when their opponents did. By the 40s BC the civil calendar was months out of step with the seasons.

Julius Caesar fixes the length but not February

In 46 BC Julius Caesar, on the advice of the astronomer Sosigenes, stretched that year to 445 days to realign it with the sun. From 45 BC the new Julian calendar had 365 days with a leap day every fourth year. Caesar found the extra ten days by lengthening the 29-day months:

February was left at 28, and the leap day went into February because that was where intercalation had always happened. The Romans did not add a February 29. They counted February 24 twice, which is why a leap year is also called a bissextile year.

The Augustus story is a myth

A popular story says February once had 29 or 30 days and that Augustus took a day from it so that his month, August, would be as long as Julius Caesar's July. There is no ancient evidence for it. August already had 31 days after Caesar's reform, decades before Sextilis was renamed for Augustus in 8 BC. The tale is usually traced to the medieval scholar Johannes de Sacrobosco in the 13th century.

February today

The Gregorian calendar of 1582 changed only the leap year rule, not the month lengths, so February still has 28 days in common years and 29 in leap years. The next February 29 is in 2028; the rules for which years qualify are in is 2028 a leap year.

A 28-day February is also the only month that can fill exactly four rows on a calendar grid, which happens when February 1 lands on the first day of your week. February 2026 starts on a Sunday, so it fits in four rows on a Sunday-first calendar, and February 2027 starts on a Monday, so it does the same on a Monday-first calendar. Plenty of people print short months for this reason: build one in the builder and you get room for notes below the grid. For the full set of month layouts, see the monthly templates, and for how the leftover days add up across a year, read how many weeks are in a year.