—

              
package Time::Zone;
HideShow 38 lines of Pod
=head1 NAME
Time::Zone -- miscellaneous timezone manipulations routines
=head1 SYNOPSIS
        use Time::Zone;
        print tz2zone();
        print tz2zone($ENV{'TZ'});
        print tz2zone($ENV{'TZ'}, time());
        print tz2zone($ENV{'TZ'}, undef, $isdst);
        $offset = tz_local_offset();
        $offset = tz_offset($TZ);
=head1 DESCRIPTION
This is a collection of miscellaneous timezone manipulation routines.
C<tz2zone()> parses the TZ environment variable and returns a timezone
string suitable for inclusion in L<date(1)>-like output.  It opionally takes
a timezone string, a time, and a is-dst flag.
C<tz_local_offset()> determins the offset from GMT time in seconds.  It
only does the calculation once.
C<tz_offset()> determines the offset from GMT in seconds of a specified
timezone.  
C<tz_name()> determines the name of the timezone based on its offset
=head1 AUTHORS
Graham Barr <gbarr@pobox.com>
David Muir Sharnoff <muir@idiom.com>
Paul Foley <paul@ascent.com>
=cut
require 5.002;
require Exporter;
use Carp;
use strict;
use vars qw(@ISA @EXPORT $VERSION @tz_local);
@ISA = qw(Exporter);
@EXPORT = qw(tz2zone tz_local_offset tz_offset tz_name);
$VERSION = "2.24";
# Parts stolen from code by Paul Foley <paul@ascent.com>
sub tz2zone (;$$$)
{
        my($TZ, $time, $isdst) = @_;
        use vars qw(%tzn_cache);
        $TZ = defined($ENV{'TZ'}) ? ( $ENV{'TZ'} ? $ENV{'TZ'} : 'GMT' ) : ''
            unless $TZ;
        # Hack to deal with 'PST8PDT' format of TZ
        # Note that this can't deal with all the esoteric forms, but it
        # does recognize the most common: [:]STDoff[DST[off][,rule]]
        if (! defined $isdst) {
                my $j;
                $time = time() unless $time;
                ($j, $j, $j, $j, $j, $j, $j, $j, $isdst) = localtime($time);
        }
        if (defined $tzn_cache{$TZ}->[$isdst]) {
                return $tzn_cache{$TZ}->[$isdst];
        }
       
        if ($TZ =~ /^
                    ( [^:\d+\-,] {3,} )
                    ( [+-] ?
                      \d {1,2}
                      ( : \d {1,2} ) {0,2} 
                    )
                    ( [^\d+\-,] {3,} )?
                    /x
            ) {
                my $dsttz = defined($4) ? $4 : $1;
                $TZ = $isdst ? $dsttz : $1;
                $tzn_cache{$TZ} = [ $1, $dsttz ];
        } else {
                $tzn_cache{$TZ} = [ $TZ, $TZ ];
        }
        return $TZ;
}
sub tz_local_offset (;$)
{
        my ($time) = @_;
        $time = time() unless $time;
        my (@l) = localtime($time);
        my $isdst = $l[8];
        if (defined($tz_local[$isdst])) {
                return $tz_local[$isdst];
        }
        $tz_local[$isdst] = &calc_off($time);
        return $tz_local[$isdst];
}
sub calc_off
{
        my ($time) = @_;
        my (@l) = localtime($time);
        my (@g) = gmtime($time);
        my $off;
        $off =     $l[0] - $g[0]
                + ($l[1] - $g[1]) * 60
                + ($l[2] - $g[2]) * 3600;
        # subscript 7 is yday.
        if ($l[7] == $g[7]) {
                # done
        } elsif ($l[7] == $g[7] + 1) {
                $off += 86400;
        } elsif ($l[7] == $g[7] - 1) {
                $off -= 86400;
        } elsif ($l[7] < $g[7]) {
                # crossed over a year boundry!
                # localtime is beginning of year, gmt is end
                # therefore local is ahead
                $off += 86400;
        } else {
                $off -= 86400;
        }
        return $off;
}
# constants
CONFIG: {
        use vars qw(%dstZone %zoneOff %dstZoneOff %Zone);
        my @dstZone = (
        #   "ndt"  =>   -2*3600-1800,         # Newfoundland Daylight   
            "brst" =>   -2*3600,         # Brazil Summer Time (East Daylight)
            "adt"  =>   -3*3600,      # Atlantic Daylight   
            "edt"  =>   -4*3600,      # Eastern Daylight
            "cdt"  =>   -5*3600,      # Central Daylight
            "mdt"  =>   -6*3600,      # Mountain Daylight
            "pdt"  =>   -7*3600,      # Pacific Daylight
            "akdt" =>   -8*3600,         # Alaska Daylight
            "ydt"  =>   -8*3600,      # Yukon Daylight
            "hdt"  =>   -9*3600,      # Hawaii Daylight
            "bst"  =>   +1*3600,      # British Summer   
            "mest" =>   +2*3600,      # Middle European Summer   
            "metdst" => +2*3600,      # Middle European DST
            "sst"  =>   +2*3600,      # Swedish Summer
            "fst"  =>   +2*3600,      # French Summer
            "cest" =>   +2*3600,         # Central European Daylight
            "eest" =>   +3*3600,         # Eastern European Summer
            "msd"  =>   +4*3600,         # Moscow Daylight
            "wadt" =>   +8*3600,      # West Australian Daylight
            "kdt"  =>  +10*3600,      # Korean Daylight
        #   "cadt" =>  +10*3600+1800,         # Central Australian Daylight
            "aedt" =>  +11*3600,      # Eastern Australian Daylight
            "eadt" =>  +11*3600,      # Eastern Australian Daylight
            "nzd"  =>  +13*3600,      # New Zealand Daylight   
            "nzdt" =>  +13*3600,      # New Zealand Daylight   
        );
        my @Zone = (
            "gmt"       =>   0,       # Greenwich Mean
            "ut"        =>   0,       # Universal (Coordinated)
            "utc"       =>   0,
            "wet"       =>   0,       # Western European
            "wat"       =>  -1*3600,  # West Africa
            "at"        =>  -2*3600,  # Azores
            "fnt"       =>  -2*3600,  # Brazil Time (Extreme East - Fernando Noronha)
            "brt"       =>  -3*3600,  # Brazil Time (East Standard - Brasilia)
        # For completeness.  BST is also British Summer, and GST is also Guam Standard.
        #   "bst"       =>  -3*3600,  # Brazil Standard
        #   "gst"       =>  -3*3600,  # Greenland Standard
        #   "nft"       =>  -3*3600-1800,# Newfoundland
        #   "nst"       =>  -3*3600-1800,# Newfoundland Standard
            "mnt"       =>  -4*3600,  # Brazil Time (West Standard - Manaus)
            "ewt"       =>  -4*3600,  # U.S. Eastern War Time
            "ast"       =>  -4*3600,  # Atlantic Standard
            "est"       =>  -5*3600,  # Eastern Standard
            "act"       =>  -5*3600,  # Brazil Time (Extreme West - Acre)
            "cst"       =>  -6*3600,  # Central Standard
            "mst"       =>  -7*3600,  # Mountain Standard
            "pst"       =>  -8*3600,  # Pacific Standard
            "akst"      =>  -9*3600,     # Alaska Standard
            "yst"       =>  -9*3600,  # Yukon Standard
            "hst"       => -10*3600,  # Hawaii Standard
            "cat"       => -10*3600,  # Central Alaska
            "ahst"      => -10*3600,  # Alaska-Hawaii Standard
            "nt"        => -11*3600,  # Nome
            "idlw"      => -12*3600,  # International Date Line West
            "cet"       =>  +1*3600,          # Central European
            "mez"       =>  +1*3600,          # Central European (German)
            "ect"       =>  +1*3600,          # Central European (French)
            "met"       =>  +1*3600,          # Middle European
            "mewt"      =>  +1*3600,          # Middle European Winter
            "swt"       =>  +1*3600,          # Swedish Winter
            "set"       =>  +1*3600,          # Seychelles
            "fwt"       =>  +1*3600,          # French Winter
            "eet"       =>  +2*3600,          # Eastern Europe, USSR Zone 1
            "ukr"       =>  +2*3600,          # Ukraine
            "bt"        =>  +3*3600,          # Baghdad, USSR Zone 2
            "msk"       =>  +3*3600,     # Moscow
        #   "it"        =>  +3*3600+1800,# Iran
            "zp4"       =>  +4*3600,          # USSR Zone 3
            "zp5"       =>  +5*3600,          # USSR Zone 4
        #   "ist"       =>  +5*3600+1800,# Indian Standard
            "zp6"       =>  +6*3600,          # USSR Zone 5
        # For completeness.  NST is also Newfoundland Stanard, and SST is also Swedish Summer.
        #   "nst"       =>  +6*3600+1800,# North Sumatra
        #   "sst"       =>  +7*3600,          # South Sumatra, USSR Zone 6
        #   "jt"        =>  +7*3600+1800,# Java (3pm in Cronusland!)
            "wst"       =>  +8*3600,          # West Australian Standard
            "hkt"       =>  +8*3600,          # Hong Kong
            "cct"       =>  +8*3600,          # China Coast, USSR Zone 7
            "jst"       =>  +9*3600,  # Japan Standard, USSR Zone 8
            "kst"       =>  +9*3600,  # Korean Standard
        #   "cast"      =>  +9*3600+1800,# Central Australian Standard
            "aest"      => +10*3600,  # Eastern Australian Standard
            "east"      => +10*3600,  # Eastern Australian Standard
            "gst"       => +10*3600,  # Guam Standard, USSR Zone 9
            "nzt"       => +12*3600,  # New Zealand
            "nzst"      => +12*3600,  # New Zealand Standard
            "idle"      => +12*3600,  # International Date Line East
        );
        %Zone = @Zone;
        %dstZone = @dstZone;
        %zoneOff = reverse(@Zone);
        %dstZoneOff = reverse(@dstZone);
}
sub tz_offset (;$$)
{
        my ($zone, $time) = @_;
        return &tz_local_offset($time) unless($zone);
        $time = time() unless $time;
        my(@l) = localtime($time);
        my $dst = $l[8];
        $zone = lc $zone;
        if($zone =~ /^(([\-\+])\d\d?)(\d\d)$/) {
                my $v = $2 . $3;
                return $1 * 3600 + $v * 60;
        } elsif (exists $dstZone{$zone} && ($dst || !exists $Zone{$zone})) {
                return $dstZone{$zone};
        } elsif(exists $Zone{$zone}) {
                return $Zone{$zone};
        }
        undef;
}
sub tz_name (;$$)
{
        my ($off, $dst) = @_;
        $off = tz_offset()
                unless(defined $off);
        $dst = (localtime(time))[8]
                unless(defined $dst);
        if (exists $dstZoneOff{$off} && ($dst || !exists $zoneOff{$off})) {
                return $dstZoneOff{$off};
        } elsif (exists $zoneOff{$off}) {
                return $zoneOff{$off};
        }
        sprintf("%+05d", int($off / 60) * 100 + $off % 60);
}
1;