IsLeapYear Function

public function IsLeapYear(year) result(isLeap)

Returns true if the specified year is a leap year

Method:

In the Gregorian calendar, a normal year consists of 365 days. Because the actual length of a sidereal year (the time required for the Earth to revolve once about the Sun) is actually 365.25635 days, a "leap year" of 366 days is used once every four years to eliminate the error caused by three normal (but short) years. Any year that is evenly divisible by 4 is a leap year: for example, 1988, 1992, and 1996 are leap years. However, there is still a small error that must be accounted for. To eliminate this error, the Gregorian calendar stipulates that a year that is evenly divisible by 100 (for example, 1900) is a leap year only if it is also evenly divisible by 400. For this reason, the following years are not leap years: 1700, 1800, 1900, 2100, 2200, 2300, 2500, 2600 This is because they are evenly divisible by 100 but not by 400. The following years are leap years: 1600, 2000, 2400 This is because they are evenly divisible by both 100 and 400.

Arguments

Return Value logical

FUNCTION IsLeapYear &
!
(year) &
!
RESULT (isLeap)

IMPLICIT NONE

! Arguments with intent(in):
INTEGER (KIND = short), INTENT(IN) :: year

! Local variables:
LOGICAL :: isLeap
!------------end of declaration------------------------------------------------

IF ( MOD ( year, 4 ) == 0 ) THEN
  IF ( MOD ( year, 400) > 0 .AND. MOD ( year, 100) == 0 ) THEN
     isLeap = .FALSE.
  ELSE
     isLeap = .TRUE.
  END IF
ELSE
  isLeap = .FALSE.
END IF 

END FUNCTION IsLeapYear