How Many Days Are In February?

February has 28 days in common years and 29 days in leap years. The Gregorian leap-year rule, ratified by Pope Gregory XIII's bull Inter gravissimas on 24 February 1582, says: a year is leap if divisible by 4, except century years not divisible by 400. So 2028, 2032, 2036 are leap; 2026 is not; 1900 was not; 2000 was. February 2026 has 28 days because 2026 is not divisible by 4 (2026 / 4 = 506.5).

February is the shortest month in the Gregorian calendar. Its name derives from the Latin februum meaning ‘purification’, referring to the Roman purification ritual Februa held on the 15th day of the month in the Roman lunar calendar. The Roman king Numa Pompilius added January and February to the original 10-month Roman calendar around 713 BCE, making the year 355 days. Caesar's 46 BCE reform brought it close to the modern 365-day length.

Until 1582, the entire Western world used the Julian calendar (introduced by Julius Caesar in 46 BCE), which inserted a leap day every fourth year without exception. This made the Julian average year 365.25 days, overshooting the true tropical year of 365.2422 days by 11 minutes 14 seconds per year. By 1582 the calendar had drifted ten days behind the seasons, so the Gregorian reform dropped 10 days from October 1582 and tightened the leap rule to its modern form. Protestant nations resisted the reform for centuries (Britain adopted it in 1752, Russia in 1918).

29 February is the leap day. People born on 29 February (leaplings or leapers) celebrate their birthday on 28 February in common years in some legal jurisdictions and on 1 March in others. There are approximately 5 million leaplings worldwide. The chance of being born on 29 February is about 1 in 1,461. The Honor Society of Leap Year Day Babies (operating since 1988) coordinates global leapling celebrations every four years.

Year 2026, our current year, is NOT a leap year. February 2026 starts on Sunday 1 February and ends on Saturday 28 February. It contains four full weeks plus the leading Sunday boundary, with 4 Sundays, 4 Mondays, 4 Tuesdays, 4 Wednesdays, 4 Thursdays, 4 Fridays, and 4 Saturdays. February 2024 was a leap February (29 days) and started on a Thursday. February 2028 will be the next leap February (29 days) and will start on a Tuesday.

The astronomical basis for the leap-day mechanism is Earth's orbital period around the Sun, the tropical year, which is 365.2422 mean solar days. The Gregorian calendar approximates this with an average of 365.2425 days, achieved by inserting 97 leap days every 400 years (instead of 100 under the Julian rule). The remaining 0.0003-day-per-year drift is small enough that the calendar will not need correction for several thousand years. NIST in Boulder, Colorado, and the US Naval Observatory monitor the tropical year via VLBI observations of distant quasars.

Modern timezone software, including the February grid SVG rendered above, draws on the IANA Time Zone Database and the JavaScript Date API. Every Linux, macOS, iOS, Android, and modern browser correctly handles 29 February in leap years via the Gregorian leap-rule logic compiled into its standard library. The ISO 8601 standard codifies the date format YYYY-MM-DD; 29 February in a non-leap year is an invalid date and is rejected by all conforming date parsers.

Citation footnotes: the Gregorian calendar leap-year rule appears in the 1582 papal bull Inter gravissimas and is codified in modern law via the UK Calendar (New Style) Act 1750 (adopted 1752) and equivalent statutes worldwide. ISO 8601:2019 (International Organization for Standardization) is the current international standard. The Honor Society of Leap Year Day Babies maintains leapyearday.com. NIST and USNO publish tropical-year measurements based on VLBI observations published in the IERS Annual Report.