9 use vars qw( $VERSION @ISA @EXPORT @EXPORT_OK );
12 @ISA = qw( Exporter );
13 @EXPORT = qw( timegm timelocal );
14 @EXPORT_OK = qw( timegm_nocheck timelocal_nocheck );
16 my @MonthDays = ( 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 );
18 # Determine breakpoint for rolling century
19 my $ThisYear = ( localtime() )[5];
20 my $Breakpoint = ( $ThisYear + 50 ) % 100;
21 my $NextCentury = $ThisYear - $ThisYear % 100;
22 $NextCentury += 100 if $Breakpoint < 50;
23 my $Century = $NextCentury - 100;
26 my ( %Options, %Cheat );
28 use constant SECS_PER_MINUTE => 60;
29 use constant SECS_PER_HOUR => 3600;
30 use constant SECS_PER_DAY => 86400;
32 my $MaxInt = ( ( 1 << ( 8 * $Config{ivsize} - 2 ) ) - 1 ) * 2 + 1;
33 my $MaxDay = int( ( $MaxInt - ( SECS_PER_DAY / 2 ) ) / SECS_PER_DAY ) - 1;
35 if ( $^O eq 'MacOS' ) {
36 # time_t is unsigned...
37 $MaxInt = ( 1 << ( 8 * $Config{ivsize} ) ) - 1;
40 # Determine the EPOC day for this machine
43 # work around posix-977 -- VOS doesn't handle dates in the range
45 $Epoc = _daygm( 0, 0, 0, 1, 0, 70, 4, 0 );
47 elsif ( $^O eq 'MacOS' ) {
48 $MaxDay *=2 if $^O eq 'MacOS'; # time_t unsigned ... quick hack?
49 # MacOS time() is seconds since 1 Jan 1904, localtime
50 # so we need to calculate an offset to apply later
52 $SecOff = timelocal( localtime(0)) - timelocal( gmtime(0) ) ;
53 $Epoc += _daygm( gmtime(0) );
56 $Epoc = _daygm( gmtime(0) );
59 %Cheat = (); # clear the cache as epoc has changed
63 # This is written in such a byzantine way in order to avoid
64 # lexical variables and sub calls, for speed
66 $Cheat{ pack( 'ss', @_[ 4, 5 ] ) } ||= do {
67 my $month = ( $_[4] + 10 ) % 12;
68 my $year = $_[5] + 1900 - $month / 10;
74 + ( ( ( $month * 306 ) + 5 ) / 10 )
83 $SecOff + $_[0] + ( SECS_PER_MINUTE * $_[1] ) + ( SECS_PER_HOUR * $_[2] );
85 return $sec + ( SECS_PER_DAY * &_daygm );
89 my ( $sec, $min, $hour, $mday, $month, $year ) = @_;
91 if ( $year >= 1000 ) {
94 elsif ( $year < 100 and $year >= 0 ) {
95 $year += ( $year > $Breakpoint ) ? $Century : $NextCentury;
98 unless ( $Options{no_range_check} ) {
99 if ( abs($year) >= 0x7fff ) {
102 "Cannot handle date ($sec, $min, $hour, $mday, $month, *$year*)";
105 croak "Month '$month' out of range 0..11"
109 my $md = $MonthDays[$month];
111 if $month == 1 && _is_leap_year( $year + 1900 );
113 croak "Day '$mday' out of range 1..$md" if $mday > $md or $mday < 1;
114 croak "Hour '$hour' out of range 0..23" if $hour > 23 or $hour < 0;
115 croak "Minute '$min' out of range 0..59" if $min > 59 or $min < 0;
116 croak "Second '$sec' out of range 0..59" if $sec > 59 or $sec < 0;
119 my $days = _daygm( undef, undef, undef, $mday, $month, $year );
121 unless ($Options{no_range_check} or abs($days) < $MaxDay) {
123 $msg .= "Day too big - $days > $MaxDay\n" if $days > $MaxDay;
126 $msg .= "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)";
133 + ( SECS_PER_MINUTE * $min )
134 + ( SECS_PER_HOUR * $hour )
135 + ( SECS_PER_DAY * $days );
139 return 0 if $_[0] % 4;
140 return 1 if $_[0] % 100;
141 return 0 if $_[0] % 400;
147 local $Options{no_range_check} = 1;
153 my $loc_for_ref_t = _timegm( localtime($ref_t) );
155 my $zone_off = $loc_for_ref_t - $ref_t
156 or return $loc_for_ref_t;
158 # Adjust for timezone
159 my $loc_t = $ref_t - $zone_off;
161 # Are we close to a DST change or are we done
162 my $dst_off = $ref_t - _timegm( localtime($loc_t) );
164 # If this evaluates to true, it means that the value in $loc_t is
165 # the _second_ hour after a DST change where the local time moves
168 ( ( $ref_t - SECS_PER_HOUR ) - _timegm( localtime( $loc_t - SECS_PER_HOUR ) ) < 0 )
170 return $loc_t - SECS_PER_HOUR;
173 # Adjust for DST change
176 return $loc_t if $dst_off > 0;
178 # If the original date was a non-extent gap in a forward DST jump,
179 # we should now have the wrong answer - undo the DST adjustment
180 my ( $s, $m, $h ) = localtime($loc_t);
181 $loc_t -= $dst_off if $s != $_[0] || $m != $_[1] || $h != $_[2];
186 sub timelocal_nocheck {
187 local $Options{no_range_check} = 1;
197 Time::Local - efficiently compute time from local and GMT time
201 $time = timelocal($sec,$min,$hour,$mday,$mon,$year);
202 $time = timegm($sec,$min,$hour,$mday,$mon,$year);
206 This module provides functions that are the inverse of built-in perl
207 functions C<localtime()> and C<gmtime()>. They accept a date as a
208 six-element array, and return the corresponding C<time(2)> value in
209 seconds since the system epoch (Midnight, January 1, 1970 GMT on Unix,
210 for example). This value can be positive or negative, though POSIX
211 only requires support for positive values, so dates before the
212 system's epoch may not work on all operating systems.
214 It is worth drawing particular attention to the expected ranges for
215 the values provided. The value for the day of the month is the actual
216 day (ie 1..31), while the month is the number of months since January
217 (0..11). This is consistent with the values returned from
218 C<localtime()> and C<gmtime()>.
222 =head2 C<timelocal()> and C<timegm()>
224 This module exports two functions by default, C<timelocal()> and
227 The C<timelocal()> and C<timegm()> functions perform range checking on
228 the input $sec, $min, $hour, $mday, and $mon values by default.
230 =head2 C<timelocal_nocheck()> and C<timegm_nocheck()>
232 If you are working with data you know to be valid, you can speed your
233 code up by using the "nocheck" variants, C<timelocal_nocheck()> and
234 C<timegm_nocheck()>. These variants must be explicitly imported.
236 use Time::Local 'timelocal_nocheck';
238 # The 365th day of 1999
239 print scalar localtime timelocal_nocheck 0,0,0,365,0,99;
241 If you supply data which is not valid (month 27, second 1,000) the
242 results will be unpredictable (so don't do that).
244 =head2 Year Value Interpretation
246 Strictly speaking, the year should be specified in a form consistent
247 with C<localtime()>, i.e. the offset from 1900. In order to make the
248 interpretation of the year easier for humans, however, who are more
249 accustomed to seeing years as two-digit or four-digit values, the
250 following conventions are followed:
256 Years greater than 999 are interpreted as being the actual year,
257 rather than the offset from 1900. Thus, 1964 would indicate the year
258 Martin Luther King won the Nobel prize, not the year 3864.
262 Years in the range 100..999 are interpreted as offset from 1900, so
263 that 112 indicates 2012. This rule also applies to years less than
264 zero (but see note below regarding date range).
268 Years in the range 0..99 are interpreted as shorthand for years in the
269 rolling "current century," defined as 50 years on either side of the
270 current year. Thus, today, in 1999, 0 would refer to 2000, and 45 to
271 2045, but 55 would refer to 1955. Twenty years from now, 55 would
272 instead refer to 2055. This is messy, but matches the way people
273 currently think about two digit dates. Whenever possible, use an
274 absolute four digit year instead.
278 The scheme above allows interpretation of a wide range of dates,
279 particularly if 4-digit years are used.
281 =head2 Limits of time_t
283 The range of dates that can be actually be handled depends on the size
284 of C<time_t> (usually a signed integer) on the given
285 platform. Currently, this is 32 bits for most systems, yielding an
286 approximate range from Dec 1901 to Jan 2038.
288 Both C<timelocal()> and C<timegm()> croak if given dates outside the
291 =head2 Ambiguous Local Times (DST)
293 Because of DST changes, there are many time zones where the same local
294 time occurs for two different GMT times on the same day. For example,
295 in the "Europe/Paris" time zone, the local time of 2001-10-28 02:30:00
296 can represent either 2001-10-28 00:30:00 GMT, B<or> 2001-10-28
299 When given an ambiguous local time, the timelocal() function should
300 always return the epoch for the I<earlier> of the two possible GMT
303 =head2 Non-Existent Local Times (DST)
305 When a DST change causes a locale clock to skip one hour forward,
306 there will be an hour's worth of local times that don't exist. Again,
307 for the "Europe/Paris" time zone, the local clock jumped from
308 2001-03-25 01:59:59 to 2001-03-25 03:00:00.
310 If the C<timelocal()> function is given a non-existent local time, it
311 will simply return an epoch value for the time one hour later.
313 =head2 Negative Epoch Values
315 Negative epoch (C<time_t>) values are not officially supported by the
316 POSIX standards, so this module's tests do not test them. On some
317 systems, they are known not to work. These include MacOS (pre-OSX) and
320 On systems which do support negative epoch values, this module should
321 be able to cope with dates before the start of the epoch, down the
322 minimum value of time_t for the system.
324 =head1 IMPLEMENTATION
326 These routines are quite efficient and yet are always guaranteed to
327 agree with C<localtime()> and C<gmtime()>. We manage this by caching
328 the start times of any months we've seen before. If we know the start
329 time of the month, we can always calculate any time within the month.
330 The start times are calculated using a mathematical formula. Unlike
331 other algorithms that do multiple calls to C<gmtime()>.
333 The C<timelocal()> function is implemented using the same cache. We
334 just assume that we're translating a GMT time, and then fudge it when
335 we're done for the timezone and daylight savings arguments. Note that
336 the timezone is evaluated for each date because countries occasionally
337 change their official timezones. Assuming that C<localtime()> corrects
338 for these changes, this routine will also be correct.
342 The whole scheme for interpreting two-digit years can be considered a
347 Support for this module is provided via the datetime@perl.org email
348 list. See http://lists.perl.org/ for more details.
350 Please submit bugs to the CPAN RT system at
351 http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Time-Local or via email
352 at bug-time-local@rt.cpan.org.
356 Copyright (c) 1997-2003 Graham Barr, 2003-2007 David Rolsky. All
357 rights reserved. This program is free software; you can redistribute
358 it and/or modify it under the same terms as Perl itself.
360 The full text of the license can be found in the LICENSE file included
365 This module is based on a Perl 4 library, timelocal.pl, that was
366 included with Perl 4.036, and was most likely written by Tom
369 The current version was written by Graham Barr.
371 It is now being maintained separately from the Perl core by Dave
372 Rolsky, <autarch@urth.org>.