8 use vars qw( $VERSION @ISA @EXPORT @EXPORT_OK );
11 @ISA = qw( Exporter );
12 @EXPORT = qw( timegm timelocal );
13 @EXPORT_OK = qw( timegm_nocheck timelocal_nocheck );
15 my @MonthDays = ( 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 );
17 # Determine breakpoint for rolling century
18 my $ThisYear = ( localtime() )[5];
19 my $Breakpoint = ( $ThisYear + 50 ) % 100;
20 my $NextCentury = $ThisYear - $ThisYear % 100;
21 $NextCentury += 100 if $Breakpoint < 50;
22 my $Century = $NextCentury - 100;
25 my ( %Options, %Cheat );
27 use constant SECS_PER_MINUTE => 60;
28 use constant SECS_PER_HOUR => 3600;
29 use constant SECS_PER_DAY => 86400;
31 # localtime()'s limit is the year 2**31
32 my $MaxDay = 365 * (2**31);
34 # Determine the EPOC day for this machine
37 # work around posix-977 -- VOS doesn't handle dates in the range
39 $Epoc = _daygm( 0, 0, 0, 1, 0, 70, 4, 0 );
41 elsif ( $^O eq 'MacOS' ) {
42 $MaxDay *=2 if $^O eq 'MacOS'; # time_t unsigned ... quick hack?
43 # MacOS time() is seconds since 1 Jan 1904, localtime
44 # so we need to calculate an offset to apply later
46 $SecOff = timelocal( localtime(0)) - timelocal( gmtime(0) ) ;
47 $Epoc += _daygm( gmtime(0) );
50 $Epoc = _daygm( gmtime(0) );
53 %Cheat = (); # clear the cache as epoc has changed
57 # This is written in such a byzantine way in order to avoid
58 # lexical variables and sub calls, for speed
60 $Cheat{ pack( 'ss', @_[ 4, 5 ] ) } ||= do {
61 my $month = ( $_[4] + 10 ) % 12;
62 my $year = $_[5] + 1900 - int($month / 10);
68 + int( ( ( $month * 306 ) + 5 ) / 10 )
77 $SecOff + $_[0] + ( SECS_PER_MINUTE * $_[1] ) + ( SECS_PER_HOUR * $_[2] );
79 return $sec + ( SECS_PER_DAY * &_daygm );
83 my ( $sec, $min, $hour, $mday, $month, $year ) = @_;
85 if ( $year >= 1000 ) {
88 elsif ( $year < 100 and $year >= 0 ) {
89 $year += ( $year > $Breakpoint ) ? $Century : $NextCentury;
92 unless ( $Options{no_range_check} ) {
93 croak "Month '$month' out of range 0..11"
97 my $md = $MonthDays[$month];
99 if $month == 1 && _is_leap_year( $year + 1900 );
101 croak "Day '$mday' out of range 1..$md" if $mday > $md or $mday < 1;
102 croak "Hour '$hour' out of range 0..23" if $hour > 23 or $hour < 0;
103 croak "Minute '$min' out of range 0..59" if $min > 59 or $min < 0;
104 croak "Second '$sec' out of range 0..59" if $sec > 59 or $sec < 0;
107 my $days = _daygm( undef, undef, undef, $mday, $month, $year );
109 unless ($Options{no_range_check} or abs($days) < $MaxDay) {
111 $msg .= "Day too big - $days > $MaxDay\n" if $days > $MaxDay;
114 $msg .= "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)";
121 + ( SECS_PER_MINUTE * $min )
122 + ( SECS_PER_HOUR * $hour )
123 + ( SECS_PER_DAY * $days );
127 return 0 if $_[0] % 4;
128 return 1 if $_[0] % 100;
129 return 0 if $_[0] % 400;
135 local $Options{no_range_check} = 1;
141 my $loc_for_ref_t = _timegm( localtime($ref_t) );
143 my $zone_off = $loc_for_ref_t - $ref_t
144 or return $loc_for_ref_t;
146 # Adjust for timezone
147 my $loc_t = $ref_t - $zone_off;
149 # Are we close to a DST change or are we done
150 my $dst_off = $ref_t - _timegm( localtime($loc_t) );
152 # If this evaluates to true, it means that the value in $loc_t is
153 # the _second_ hour after a DST change where the local time moves
156 ( ( $ref_t - SECS_PER_HOUR ) - _timegm( localtime( $loc_t - SECS_PER_HOUR ) ) < 0 )
158 return $loc_t - SECS_PER_HOUR;
161 # Adjust for DST change
164 return $loc_t if $dst_off > 0;
166 # If the original date was a non-extent gap in a forward DST jump,
167 # we should now have the wrong answer - undo the DST adjustment
168 my ( $s, $m, $h ) = localtime($loc_t);
169 $loc_t -= $dst_off if $s != $_[0] || $m != $_[1] || $h != $_[2];
174 sub timelocal_nocheck {
175 local $Options{no_range_check} = 1;
185 Time::Local - efficiently compute time from local and GMT time
189 $time = timelocal($sec,$min,$hour,$mday,$mon,$year);
190 $time = timegm($sec,$min,$hour,$mday,$mon,$year);
194 This module provides functions that are the inverse of built-in perl
195 functions C<localtime()> and C<gmtime()>. They accept a date as a
196 six-element array, and return the corresponding C<time(2)> value in
197 seconds since the system epoch (Midnight, January 1, 1970 GMT on Unix,
198 for example). This value can be positive or negative, though POSIX
199 only requires support for positive values, so dates before the
200 system's epoch may not work on all operating systems.
202 It is worth drawing particular attention to the expected ranges for
203 the values provided. The value for the day of the month is the actual
204 day (ie 1..31), while the month is the number of months since January
205 (0..11). This is consistent with the values returned from
206 C<localtime()> and C<gmtime()>.
210 =head2 C<timelocal()> and C<timegm()>
212 This module exports two functions by default, C<timelocal()> and
215 The C<timelocal()> and C<timegm()> functions perform range checking on
216 the input $sec, $min, $hour, $mday, and $mon values by default.
218 =head2 C<timelocal_nocheck()> and C<timegm_nocheck()>
220 If you are working with data you know to be valid, you can speed your
221 code up by using the "nocheck" variants, C<timelocal_nocheck()> and
222 C<timegm_nocheck()>. These variants must be explicitly imported.
224 use Time::Local 'timelocal_nocheck';
226 # The 365th day of 1999
227 print scalar localtime timelocal_nocheck 0,0,0,365,0,99;
229 If you supply data which is not valid (month 27, second 1,000) the
230 results will be unpredictable (so don't do that).
232 =head2 Year Value Interpretation
234 Strictly speaking, the year should be specified in a form consistent
235 with C<localtime()>, i.e. the offset from 1900. In order to make the
236 interpretation of the year easier for humans, however, who are more
237 accustomed to seeing years as two-digit or four-digit values, the
238 following conventions are followed:
244 Years greater than 999 are interpreted as being the actual year,
245 rather than the offset from 1900. Thus, 1964 would indicate the year
246 Martin Luther King won the Nobel prize, not the year 3864.
250 Years in the range 100..999 are interpreted as offset from 1900, so
251 that 112 indicates 2012. This rule also applies to years less than
252 zero (but see note below regarding date range).
256 Years in the range 0..99 are interpreted as shorthand for years in the
257 rolling "current century," defined as 50 years on either side of the
258 current year. Thus, today, in 1999, 0 would refer to 2000, and 45 to
259 2045, but 55 would refer to 1955. Twenty years from now, 55 would
260 instead refer to 2055. This is messy, but matches the way people
261 currently think about two digit dates. Whenever possible, use an
262 absolute four digit year instead.
266 The scheme above allows interpretation of a wide range of dates,
267 particularly if 4-digit years are used.
269 =head2 Ambiguous Local Times (DST)
271 Because of DST changes, there are many time zones where the same local
272 time occurs for two different GMT times on the same day. For example,
273 in the "Europe/Paris" time zone, the local time of 2001-10-28 02:30:00
274 can represent either 2001-10-28 00:30:00 GMT, B<or> 2001-10-28
277 When given an ambiguous local time, the timelocal() function should
278 always return the epoch for the I<earlier> of the two possible GMT
281 =head2 Non-Existent Local Times (DST)
283 When a DST change causes a locale clock to skip one hour forward,
284 there will be an hour's worth of local times that don't exist. Again,
285 for the "Europe/Paris" time zone, the local clock jumped from
286 2001-03-25 01:59:59 to 2001-03-25 03:00:00.
288 If the C<timelocal()> function is given a non-existent local time, it
289 will simply return an epoch value for the time one hour later.
291 =head1 IMPLEMENTATION
293 These routines are quite efficient and yet are always guaranteed to
294 agree with C<localtime()> and C<gmtime()>. We manage this by caching
295 the start times of any months we've seen before. If we know the start
296 time of the month, we can always calculate any time within the month.
297 The start times are calculated using a mathematical formula. Unlike
298 other algorithms that do multiple calls to C<gmtime()>.
300 The C<timelocal()> function is implemented using the same cache. We
301 just assume that we're translating a GMT time, and then fudge it when
302 we're done for the timezone and daylight savings arguments. Note that
303 the timezone is evaluated for each date because countries occasionally
304 change their official timezones. Assuming that C<localtime()> corrects
305 for these changes, this routine will also be correct.
309 The whole scheme for interpreting two-digit years can be considered a
314 Support for this module is provided via the datetime@perl.org email
315 list. See http://lists.perl.org/ for more details.
317 Please submit bugs to the CPAN RT system at
318 http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Time-Local or via email
319 at bug-time-local@rt.cpan.org.
323 Copyright (c) 1997-2003 Graham Barr, 2003-2007 David Rolsky. All
324 rights reserved. This program is free software; you can redistribute
325 it and/or modify it under the same terms as Perl itself.
327 The full text of the license can be found in the LICENSE file included
332 This module is based on a Perl 4 library, timelocal.pl, that was
333 included with Perl 4.036, and was most likely written by Tom
336 The current version was written by Graham Barr.
338 It is now being maintained separately from the Perl core by Dave
339 Rolsky, <autarch@urth.org>.