ISDSTIME()

Fortran version:

    INTEGER FUNCTION  ISDSTIME( JDATE )
        INTEGER, INTENT(IN   ) :: 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 and end for DST. Handles both pre-2007 (starts first Sunday in April, ends last Sunday in October) and 2007-and-after (second Sunday in March, first Sunday in November).

For Fortran-90 declarations and interface checking:

    USE M3UTILIO

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:

    ...
    USE M3UTILIO
    ...
    LOGICAL   ISDSTIME
    INTEGER   JDATE
    ...
    IF ( ISDSTIME( JDATE ) ) THEN
        !!  ...daylight savings time in effect
        ...
    ELSE
        !!  ...daylight savings time NOT in effect
        ...
    END IF
    ...

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