February 24 is the 55th day of the year in the
Gregorian calendar. There are 310 days remaining until the end of the year (311 in
leap years). This date is slightly more likely to fall on a Wednesday, Friday or Sunday (58 in 400 years each) than on Monday or Tuesday (57), and slightly less likely to occur on a Thursday or Saturday (56).
superstitious reasons, when the Romans began to
intercalate to bring their calendar into line with the
solar year, they chose not to place their extra month of
Mercedonius after February but within it.
 February 24—known in the
Roman calendar as "the sixth day before the
March"—was replaced by the first day of this month since it followed
Terminalia, the festival of the Roman god of boundaries. After the end of Mercedonius, the rest of the days of February were observed and the new year began with the first day of March. The overlaid religious festivals of February were so complicated that
Julius Caesar opted not to change it at all during his
BC calendar reform. The
extra day of his system's
leap years were located in the same place as the old intercalary month but he opted to ignore it as a date. Instead, the sixth day before the Kalends of March was simply said to last for 48 hours and all the other days continued to bear their original names. (The Roman practice of inclusive counting initially caused the priests in charge of the calendar to add the extra hours every three years instead of every four and
Augustus was obliged to omit them for a span of decades until the system was back to where it should have been.) When the extra hours finally began to be reckoned as two separate days instead of a doubled sixth ("bissextile") one, the
leap day was still taken to be the one following hard on the February 23 Terminalia.
 Although February 29 has been popularly understood as the leap day of leap years since the beginning of sequential reckoning of the days of months in the late Middle Ages, in
Britain and most other countries, no formal replacement of February 24 as the
leap day of the
Gregorian calendars has occurred. The exceptions include
Finland, who enacted legislation to move the day to February 29.
 This custom still has some effect around the world, for example with respect to
name days in Hungary.