February is the second month of the year in the Gregorian Calendar, with 28 days in regular years. In leap years February has 29 days.

February 29 is the 60th day of a leap year in the Gregorian Calendar, with 306 days remaining. A year which has a February 29 is, by definition, a leap year. This date only occurs approximately every four years, in years evenly divisible by 4, such as 1992, 1996, or 2004, with some exceptions in century years.

A century year, that is, a year which ends in two zeroes, 1800, 1900, 2000, etc., is not a leap year unless it is also evenly divisible by 400. This means that the year 2000 was a leap year and 2400 will also be one, but 1800 and 1900 were not leap years, and the years 2100, 2200, and 2300 won't be leap years either.

Those born on February 29 usually celebrate their birthdays on February 28 during non-leap years.

February 29 may be colloqially termed a leap day.

Three times in history a February 30 occurred.

Sweden (at that time Finland was part of the Swedish realm) planned to change from the Julian calendar to the Gregorian calendar, beginning in 1700 by omitting the leap days for the next 40 years. Thus 1700 was not a leap year in Sweden, however both 1704 and 1708 were leap years contrary to the plan. This brought the Swedish calendar one day ahead of the Julian calendar but still ten days behind the Gregorian calendar. This confusion was reduced when, in 1712, two leap days were added, thus giving this year a February 30. That date corresponded to February 29 in Julian and March 11 in Gregorian counting. The Swedish change to the Gregorian calendar was finally done in 1753.

In 1929 the Soviet Union introduced a revolutionary calendar in which every month had 30 days and the remaining 5 or 6 days were monthless holidays. In 1930 and 1931, it thus had a February 30, but in 1932 the months regained their old lengths.