Since, technically, a year consists of 365 days and approximately 6 hours, every four years these hours amount to a full day. In order to synchronize the Gregorian calendar with the astronomical year, a leap day(うるう日), February 29, is added to the 28-day month once every four years. As such, leap years(うるう年)are always evenly divisible by four. Persons born on a leap day are called “leaplings,” and contrary to popular myth, they do age during non-leap years.