.TZISDST - is time zone daylight savings?

Alternate Entry Name: _TZISDST

Usage:

B:
   %b/manif/t_ctrl
   type = .tzisdst(tzref);

C:
   #include <t_ctrl.h>
   int _tzisdst(_T_time_zone tzref);

Examples:

tzref = .tzqry("EST");
type = .tzisdst(tzref);

Where:

tzref

is a time zone reference value, as returned by .TZQRY.

type

indicates the type of time zone.

<0

this is a daylight time zone

=0

this is a standard time zone

>0

information is not available

Description:

.TZISDST determines if a particular time zone is standard time or daylight savings time. Time zones marked with the DST flag in the time zone definition file are considered daylight savings zones; others are standard zones.

A negative value can be returned in several cases. If the program is operating in the "error" locale or the "tzref" value was produced by passing an unknown name to .TZQRY, then .TZISDST will return a negative value. The program may be operating in the "error" locale if the time zone data file is not available, or access was suppressed by use of the .NO_TZ external.

See Also:

expl b tz

for background on time zones.

expl b lib .tzqry

for obtaining time zone reference values.

Copyright © 1996, Thinkage Ltd.