February is the shortest month of the year, with just 28 days in most years — and it’s the only month whose length changes. Every four years, it gains a 29th day, called a leap day, in what’s known as a leap year. This exists because Earth actually takes about 365.25 days to orbit the Sun, not an even 365. Adding a day roughly every four years keeps the calendar in sync with the seasons over time. The rule has a small refinement: century years (like 1900) are leap years only if divisible by 400, which is why 2000 was a leap year but 1900 was not.
The name February likely comes from Februa, an ancient Roman purification festival held around this point in the year — reflecting the month’s original position near the end of the old Roman calendar, before January and February were added to the front of the year.
Seasonally, February is deep winter across the Northern Hemisphere and high summer in the Southern Hemisphere. It’s widely known for Valentine’s Day on February 14th, a day associated with romance and affection in many countries, and in leap years it also carries the novelty of February 29th, sometimes called Leap Day.