290 lines
8.7 KiB
Perl
290 lines
8.7 KiB
Perl
package Time::Local;
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require Exporter;
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use Carp;
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use Config;
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use strict;
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use integer;
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use vars qw( $VERSION @ISA @EXPORT @EXPORT_OK );
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$VERSION = '1.07';
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@ISA = qw( Exporter );
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@EXPORT = qw( timegm timelocal );
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@EXPORT_OK = qw( timegm_nocheck timelocal_nocheck );
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my @MonthDays = (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
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# Determine breakpoint for rolling century
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my $ThisYear = (localtime())[5];
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my $Breakpoint = ($ThisYear + 50) % 100;
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my $NextCentury = $ThisYear - $ThisYear % 100;
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$NextCentury += 100 if $Breakpoint < 50;
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my $Century = $NextCentury - 100;
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my $SecOff = 0;
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my (%Options, %Cheat);
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my $MaxInt = ((1<<(8 * $Config{intsize} - 2))-1)*2 + 1;
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my $MaxDay = int(($MaxInt-43200)/86400)-1;
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# Determine the EPOC day for this machine
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my $Epoc = 0;
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if ($^O eq 'vos') {
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# work around posix-977 -- VOS doesn't handle dates in
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# the range 1970-1980.
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$Epoc = _daygm((0, 0, 0, 1, 0, 70, 4, 0));
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}
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elsif ($^O eq 'MacOS') {
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no integer;
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$MaxDay *=2 if $^O eq 'MacOS'; # time_t unsigned ... quick hack?
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# MacOS time() is seconds since 1 Jan 1904, localtime
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# so we need to calculate an offset to apply later
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$Epoc = 693901;
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$SecOff = timelocal(localtime(0)) - timelocal(gmtime(0));
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$Epoc += _daygm(gmtime(0));
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}
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else {
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$Epoc = _daygm(gmtime(0));
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}
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%Cheat=(); # clear the cache as epoc has changed
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sub _daygm {
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$_[3] + ($Cheat{pack("ss",@_[4,5])} ||= do {
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my $month = ($_[4] + 10) % 12;
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my $year = $_[5] + 1900 - $month/10;
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365*$year + $year/4 - $year/100 + $year/400 + ($month*306 + 5)/10 - $Epoc
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});
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}
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sub _timegm {
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my $sec = $SecOff + $_[0] + 60 * $_[1] + 3600 * $_[2];
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no integer;
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$sec + 86400 * &_daygm;
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}
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sub timegm {
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my ($sec,$min,$hour,$mday,$month,$year) = @_;
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if ($year >= 1000) {
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$year -= 1900;
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}
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elsif ($year < 100 and $year >= 0) {
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$year += ($year > $Breakpoint) ? $Century : $NextCentury;
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}
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unless ($Options{no_range_check}) {
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if (abs($year) >= 0x7fff) {
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$year += 1900;
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croak "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)";
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}
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croak "Month '$month' out of range 0..11" if $month > 11 or $month < 0;
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my $md = $MonthDays[$month];
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++$md unless $month != 1 or $year % 4 or !($year % 400);
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croak "Day '$mday' out of range 1..$md" if $mday > $md or $mday < 1;
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croak "Hour '$hour' out of range 0..23" if $hour > 23 or $hour < 0;
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croak "Minute '$min' out of range 0..59" if $min > 59 or $min < 0;
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croak "Second '$sec' out of range 0..59" if $sec > 59 or $sec < 0;
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}
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my $days = _daygm(undef, undef, undef, $mday, $month, $year);
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unless ($Options{no_range_check} or abs($days) < $MaxDay) {
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$year += 1900;
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croak "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)";
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}
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$sec += $SecOff + 60*$min + 3600*$hour;
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no integer;
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$sec + 86400*$days;
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}
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sub timegm_nocheck {
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local $Options{no_range_check} = 1;
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&timegm;
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}
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sub timelocal {
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no integer;
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my $ref_t = &timegm;
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my $loc_t = _timegm(localtime($ref_t));
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# Is there a timezone offset from GMT or are we done
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my $zone_off = $ref_t - $loc_t
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or return $loc_t;
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# Adjust for timezone
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$loc_t = $ref_t + $zone_off;
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# Are we close to a DST change or are we done
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my $dst_off = $ref_t - _timegm(localtime($loc_t))
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or return $loc_t;
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# Adjust for DST change
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$loc_t += $dst_off;
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# for a negative offset from GMT, and if the original date
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# was a non-extent gap in a forward DST jump, we should
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# now have the wrong answer - undo the DST adjust;
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return $loc_t if $zone_off <= 0;
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my ($s,$m,$h) = localtime($loc_t);
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$loc_t -= $dst_off if $s != $_[0] || $m != $_[1] || $h != $_[2];
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$loc_t;
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}
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sub timelocal_nocheck {
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local $Options{no_range_check} = 1;
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&timelocal;
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}
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1;
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__END__
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=head1 NAME
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Time::Local - efficiently compute time from local and GMT time
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=head1 SYNOPSIS
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$time = timelocal($sec,$min,$hour,$mday,$mon,$year);
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$time = timegm($sec,$min,$hour,$mday,$mon,$year);
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=head1 DESCRIPTION
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These routines are the inverse of built-in perl functions localtime()
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and gmtime(). They accept a date as a six-element array, and return
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the corresponding time(2) value in seconds since the system epoch
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(Midnight, January 1, 1970 UTC on Unix, for example). This value can
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be positive or negative, though POSIX only requires support for
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positive values, so dates before the system's epoch may not work on
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all operating systems.
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It is worth drawing particular attention to the expected ranges for
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the values provided. The value for the day of the month is the actual day
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(ie 1..31), while the month is the number of months since January (0..11).
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This is consistent with the values returned from localtime() and gmtime().
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The timelocal() and timegm() functions perform range checking on the
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input $sec, $min, $hour, $mday, and $mon values by default. If you'd
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rather they didn't, you can explicitly import the timelocal_nocheck()
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and timegm_nocheck() functions.
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use Time::Local 'timelocal_nocheck';
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{
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# The 365th day of 1999
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print scalar localtime timelocal_nocheck 0,0,0,365,0,99;
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# The twenty thousandth day since 1970
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print scalar localtime timelocal_nocheck 0,0,0,20000,0,70;
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# And even the 10,000,000th second since 1999!
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print scalar localtime timelocal_nocheck 10000000,0,0,1,0,99;
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}
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Your mileage may vary when trying these with minutes and hours,
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and it doesn't work at all for months.
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Strictly speaking, the year should also be specified in a form consistent
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with localtime(), i.e. the offset from 1900.
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In order to make the interpretation of the year easier for humans,
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however, who are more accustomed to seeing years as two-digit or four-digit
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values, the following conventions are followed:
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=over 4
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=item *
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Years greater than 999 are interpreted as being the actual year,
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rather than the offset from 1900. Thus, 1963 would indicate the year
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Martin Luther King won the Nobel prize, not the year 2863.
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=item *
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Years in the range 100..999 are interpreted as offset from 1900,
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so that 112 indicates 2012. This rule also applies to years less than zero
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(but see note below regarding date range).
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=item *
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Years in the range 0..99 are interpreted as shorthand for years in the
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rolling "current century," defined as 50 years on either side of the current
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year. Thus, today, in 1999, 0 would refer to 2000, and 45 to 2045,
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but 55 would refer to 1955. Twenty years from now, 55 would instead refer
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to 2055. This is messy, but matches the way people currently think about
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two digit dates. Whenever possible, use an absolute four digit year instead.
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=back
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The scheme above allows interpretation of a wide range of dates, particularly
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if 4-digit years are used.
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Please note, however, that the range of dates that can be actually be handled
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depends on the size of an integer (time_t) on a given platform.
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Currently, this is 32 bits for most systems, yielding an approximate range
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from Dec 1901 to Jan 2038.
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Both timelocal() and timegm() croak if given dates outside the supported
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range.
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=head1 IMPLEMENTATION
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These routines are quite efficient and yet are always guaranteed to agree
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with localtime() and gmtime(). We manage this by caching the start times
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of any months we've seen before. If we know the start time of the month,
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we can always calculate any time within the month. The start times
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are calculated using a mathematical formula. Unlike other algorithms
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that do multiple calls to gmtime().
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timelocal() is implemented using the same cache. We just assume that we're
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translating a GMT time, and then fudge it when we're done for the timezone
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and daylight savings arguments. Note that the timezone is evaluated for
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each date because countries occasionally change their official timezones.
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Assuming that localtime() corrects for these changes, this routine will
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also be correct.
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=head1 BUGS
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The whole scheme for interpreting two-digit years can be considered a bug.
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The proclivity to croak() is probably a bug.
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=head1 SUPPORT
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Support for this module is provided via the perl5-porters@perl.org
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email list. See http://lists.perl.org/ for more details.
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Please submit bugs using the RT system at bugs.perl.org, the perlbug
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script, or as a last resort, to the perl5-porters@perl.org list.
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=head1 AUTHOR
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This module is based on a Perl 4 library, timelocal.pl, that was
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included with Perl 4.036, and was most likely written by Tom
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Christiansen.
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The current version was written by Graham Barr.
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It is now being maintained separately from the Perl core by Dave
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Rolsky, <autarch@urth.org>.
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=cut
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