ISDSTIME()

Fortran version:

    INTEGER FUNCTION  ISDSTIME( JDATE )
        INTEGER   JDATE	!  Julian date (YYYYDDD)

No C version:

Summary:

ISDSTIME() returns TRUE if and only if daylight savings time is in effect for the Julian date JDATE, using the Zeller's-congruence algorithm to find the start (first Sunday in April) and end (last Sunday in October) for DST.

See also subroutines DAYMON(), HHMMSS(), JULIAN(), MMDDYY(), WKDAY(), and DT2STR() as well as EDSS/ Models-3 date-time manipulation programs gregdate and juldate.

Preconditions:

JDATE represented according to EDSS/Models-3 date and time conventions

Fortran Usage:

    ...
    ...
    LOGICAL   ISDSTIME
    INTEGER   JDATE
    ...
    IF ( ISDSTIME( JDATE ) ) THEN
C	    ...daylight savings time in effect
    ELSE    
C	    ...daylight savings time NOT in effect
    END IF
    ...


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