Leap Year Determination

Method for Determining Leap Years

Years whose Gregorian year number is divisible by 4 are considered leap years; however, as an exception, years divisible by 100 but not by 400 are considered common years.

Gregorian years can be used starting with 1582, and Japanese era years can be used starting with year 6 of the Meiji era, when the Gregorian calendar was adopted.