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;
33 if ( $^O eq 'MacOS' ) {
34 # time_t is unsigned...
35 $MaxInt = ( 1 << ( 8 * $Config{ivsize} ) ) - 1;
38 $MaxInt = ( ( 1 << ( 8 * $Config{ivsize} - 2 ) ) - 1 ) * 2 + 1;
41 my $MaxDay = int( ( $MaxInt - ( SECS_PER_DAY / 2 ) ) / SECS_PER_DAY ) - 1;
43 # Determine the EPOC day for this machine
46 # work around posix-977 -- VOS doesn't handle dates in the range
48 $Epoc = _daygm( 0, 0, 0, 1, 0, 70, 4, 0 );
50 elsif ( $^O eq 'MacOS' ) {
51 $MaxDay *=2 if $^O eq 'MacOS'; # time_t unsigned ... quick hack?
52 # MacOS time() is seconds since 1 Jan 1904, localtime
53 # so we need to calculate an offset to apply later
55 $SecOff = timelocal( localtime(0)) - timelocal( gmtime(0) ) ;
56 $Epoc += _daygm( gmtime(0) );
59 $Epoc = _daygm( gmtime(0) );
62 %Cheat = (); # clear the cache as epoc has changed
66 # This is written in such a byzantine way in order to avoid
67 # lexical variables and sub calls, for speed
69 $Cheat{ pack( 'ss', @_[ 4, 5 ] ) } ||= do {
70 my $month = ( $_[4] + 10 ) % 12;
71 my $year = ( $_[5] + 1900 ) - ( $month / 10 );
77 + ( ( ( $month * 306 ) + 5 ) / 10 )
86 $SecOff + $_[0] + ( SECS_PER_MINUTE * $_[1] ) + ( SECS_PER_HOUR * $_[2] );
88 return $sec + ( SECS_PER_DAY * &_daygm );
92 my ( $sec, $min, $hour, $mday, $month, $year ) = @_;
94 if ( $year >= 1000 ) {
97 elsif ( $year < 100 and $year >= 0 ) {
98 $year += ( $year > $Breakpoint ) ? $Century : $NextCentury;
101 unless ( $Options{no_range_check} ) {
102 croak "Month '$month' out of range 0..11"
106 my $md = $MonthDays[$month];
108 if $month == 1 && _is_leap_year( $year + 1900 );
110 croak "Day '$mday' out of range 1..$md" if $mday > $md or $mday < 1;
111 croak "Hour '$hour' out of range 0..23" if $hour > 23 or $hour < 0;
112 croak "Minute '$min' out of range 0..59" if $min > 59 or $min < 0;
113 croak "Second '$sec' out of range 0..59" if $sec > 59 or $sec < 0;
116 my $days = _daygm( undef, undef, undef, $mday, $month, $year );
118 unless ($Options{no_range_check} or abs($days) < $MaxDay) {
120 $msg .= "Day too big - $days > $MaxDay\n" if $days > $MaxDay;
123 $msg .= "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)";
130 + ( SECS_PER_MINUTE * $min )
131 + ( SECS_PER_HOUR * $hour )
132 + ( SECS_PER_DAY * $days );
136 return 0 if $_[0] % 4;
137 return 1 if $_[0] % 100;
138 return 0 if $_[0] % 400;
144 local $Options{no_range_check} = 1;
150 my $loc_for_ref_t = _timegm( localtime($ref_t) );
152 my $zone_off = $loc_for_ref_t - $ref_t
153 or return $loc_for_ref_t;
155 # Adjust for timezone
156 my $loc_t = $ref_t - $zone_off;
158 # Are we close to a DST change or are we done
159 my $dst_off = $ref_t - _timegm( localtime($loc_t) );
161 # If this evaluates to true, it means that the value in $loc_t is
162 # the _second_ hour after a DST change where the local time moves
165 ( ( $ref_t - SECS_PER_HOUR ) - _timegm( localtime( $loc_t - SECS_PER_HOUR ) ) < 0 )
167 return $loc_t - SECS_PER_HOUR;
170 # Adjust for DST change
173 return $loc_t if $dst_off > 0;
175 # If the original date was a non-extent gap in a forward DST jump,
176 # we should now have the wrong answer - undo the DST adjustment
177 my ( $s, $m, $h ) = localtime($loc_t);
178 $loc_t -= $dst_off if $s != $_[0] || $m != $_[1] || $h != $_[2];
183 sub timelocal_nocheck {
184 local $Options{no_range_check} = 1;
194 Time::Local - efficiently compute time from local and GMT time
198 $time = timelocal($sec,$min,$hour,$mday,$mon,$year);
199 $time = timegm($sec,$min,$hour,$mday,$mon,$year);
203 This module provides functions that are the inverse of built-in perl
204 functions C<localtime()> and C<gmtime()>. They accept a date as a
205 six-element array, and return the corresponding C<time(2)> value in
206 seconds since the system epoch (Midnight, January 1, 1970 GMT on Unix,
207 for example). This value can be positive or negative, though POSIX
208 only requires support for positive values, so dates before the
209 system's epoch may not work on all operating systems.
211 It is worth drawing particular attention to the expected ranges for
212 the values provided. The value for the day of the month is the actual
213 day (ie 1..31), while the month is the number of months since January
214 (0..11). This is consistent with the values returned from
215 C<localtime()> and C<gmtime()>.
219 =head2 C<timelocal()> and C<timegm()>
221 This module exports two functions by default, C<timelocal()> and
224 The C<timelocal()> and C<timegm()> functions perform range checking on
225 the input $sec, $min, $hour, $mday, and $mon values by default.
227 =head2 C<timelocal_nocheck()> and C<timegm_nocheck()>
229 If you are working with data you know to be valid, you can speed your
230 code up by using the "nocheck" variants, C<timelocal_nocheck()> and
231 C<timegm_nocheck()>. These variants must be explicitly imported.
233 use Time::Local 'timelocal_nocheck';
235 # The 365th day of 1999
236 print scalar localtime timelocal_nocheck 0,0,0,365,0,99;
238 If you supply data which is not valid (month 27, second 1,000) the
239 results will be unpredictable (so don't do that).
241 =head2 Year Value Interpretation
243 Strictly speaking, the year should be specified in a form consistent
244 with C<localtime()>, i.e. the offset from 1900. In order to make the
245 interpretation of the year easier for humans, however, who are more
246 accustomed to seeing years as two-digit or four-digit values, the
247 following conventions are followed:
253 Years greater than 999 are interpreted as being the actual year,
254 rather than the offset from 1900. Thus, 1964 would indicate the year
255 Martin Luther King won the Nobel prize, not the year 3864.
259 Years in the range 100..999 are interpreted as offset from 1900, so
260 that 112 indicates 2012. This rule also applies to years less than
261 zero (but see note below regarding date range).
265 Years in the range 0..99 are interpreted as shorthand for years in the
266 rolling "current century," defined as 50 years on either side of the
267 current year. Thus, today, in 1999, 0 would refer to 2000, and 45 to
268 2045, but 55 would refer to 1955. Twenty years from now, 55 would
269 instead refer to 2055. This is messy, but matches the way people
270 currently think about two digit dates. Whenever possible, use an
271 absolute four digit year instead.
275 The scheme above allows interpretation of a wide range of dates,
276 particularly if 4-digit years are used.
278 =head2 Limits of time_t
280 The range of dates that can be actually be handled depends on the size
281 of C<time_t> (usually a signed integer) on the given
282 platform. Currently, this is 32 bits for most systems, yielding an
283 approximate range from Dec 1901 to Jan 2038.
285 Both C<timelocal()> and C<timegm()> croak if given dates outside the
288 =head2 Ambiguous Local Times (DST)
290 Because of DST changes, there are many time zones where the same local
291 time occurs for two different GMT times on the same day. For example,
292 in the "Europe/Paris" time zone, the local time of 2001-10-28 02:30:00
293 can represent either 2001-10-28 00:30:00 GMT, B<or> 2001-10-28
296 When given an ambiguous local time, the timelocal() function should
297 always return the epoch for the I<earlier> of the two possible GMT
300 =head2 Non-Existent Local Times (DST)
302 When a DST change causes a locale clock to skip one hour forward,
303 there will be an hour's worth of local times that don't exist. Again,
304 for the "Europe/Paris" time zone, the local clock jumped from
305 2001-03-25 01:59:59 to 2001-03-25 03:00:00.
307 If the C<timelocal()> function is given a non-existent local time, it
308 will simply return an epoch value for the time one hour later.
310 =head2 Negative Epoch Values
312 Negative epoch (C<time_t>) values are not officially supported by the
313 POSIX standards, so this module's tests do not test them. On some
314 systems, they are known not to work. These include MacOS (pre-OSX) and
317 On systems which do support negative epoch values, this module should
318 be able to cope with dates before the start of the epoch, down the
319 minimum value of time_t for the system.
321 =head1 IMPLEMENTATION
323 These routines are quite efficient and yet are always guaranteed to
324 agree with C<localtime()> and C<gmtime()>. We manage this by caching
325 the start times of any months we've seen before. If we know the start
326 time of the month, we can always calculate any time within the month.
327 The start times are calculated using a mathematical formula. Unlike
328 other algorithms that do multiple calls to C<gmtime()>.
330 The C<timelocal()> function is implemented using the same cache. We
331 just assume that we're translating a GMT time, and then fudge it when
332 we're done for the timezone and daylight savings arguments. Note that
333 the timezone is evaluated for each date because countries occasionally
334 change their official timezones. Assuming that C<localtime()> corrects
335 for these changes, this routine will also be correct.
339 The whole scheme for interpreting two-digit years can be considered a
344 Support for this module is provided via the datetime@perl.org email
345 list. See http://lists.perl.org/ for more details.
347 Please submit bugs to the CPAN RT system at
348 http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Time-Local or via email
349 at bug-time-local@rt.cpan.org.
353 Copyright (c) 1997-2003 Graham Barr, 2003-2007 David Rolsky. All
354 rights reserved. This program is free software; you can redistribute
355 it and/or modify it under the same terms as Perl itself.
357 The full text of the license can be found in the LICENSE file included
362 This module is based on a Perl 4 library, timelocal.pl, that was
363 included with Perl 4.036, and was most likely written by Tom
366 The current version was written by Graham Barr.
368 It is now being maintained separately from the Perl core by Dave
369 Rolsky, <autarch@urth.org>.