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{intsize} - 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{intsize} ) ) - 1;
40 $MaxInt = ( ( 1 << ( 8 * $Config{intsize} - 2 ) ) - 1 ) * 2 + 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 ( $Options{no_range_check} ) {
102 if ( abs($year) >= 0x7fff ) {
105 "Cannot handle date ($sec, $min, $hour, $mday, $month, *$year*)";
108 croak "Month '$month' out of range 0..11"
112 my $md = $MonthDays[$month];
114 if $month == 1 && _is_leap_year( $year + 1900 );
116 croak "Day '$mday' out of range 1..$md" if $mday > $md or $mday < 1;
117 croak "Hour '$hour' out of range 0..23" if $hour > 23 or $hour < 0;
118 croak "Minute '$min' out of range 0..59" if $min > 59 or $min < 0;
119 croak "Second '$sec' out of range 0..59" if $sec > 59 or $sec < 0;
122 my $days = _daygm( undef, undef, undef, $mday, $month, $year );
124 unless ($Options{no_range_check} or abs($days) < $MaxDay) {
126 $msg .= "Day too big - $days > $MaxDay\n" if $days > $MaxDay;
129 $msg .= "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)";
136 + ( SECS_PER_MINUTE * $min )
137 + ( SECS_PER_HOUR * $hour )
138 + ( SECS_PER_DAY * $days );
142 return 0 if $_[0] % 4;
143 return 1 if $_[0] % 100;
144 return 0 if $_[0] % 400;
150 local $Options{no_range_check} = 1;
156 my $loc_for_ref_t = _timegm( localtime($ref_t) );
158 my $zone_off = $loc_for_ref_t - $ref_t
159 or return $loc_for_ref_t;
161 # Adjust for timezone
162 my $loc_t = $ref_t - $zone_off;
164 # Are we close to a DST change or are we done
165 my $dst_off = $ref_t - _timegm( localtime($loc_t) );
167 # If this evaluates to true, it means that the value in $loc_t is
168 # the _second_ hour after a DST change where the local time moves
171 ( ( $ref_t - SECS_PER_HOUR ) - _timegm( localtime( $loc_t - SECS_PER_HOUR ) ) < 0 )
173 return $loc_t - SECS_PER_HOUR;
176 # Adjust for DST change
179 return $loc_t if $dst_off > 0;
181 # If the original date was a non-extent gap in a forward DST jump,
182 # we should now have the wrong answer - undo the DST adjustment
183 my ( $s, $m, $h ) = localtime($loc_t);
184 $loc_t -= $dst_off if $s != $_[0] || $m != $_[1] || $h != $_[2];
189 sub timelocal_nocheck {
190 local $Options{no_range_check} = 1;
200 Time::Local - efficiently compute time from local and GMT time
204 $time = timelocal($sec,$min,$hour,$mday,$mon,$year);
205 $time = timegm($sec,$min,$hour,$mday,$mon,$year);
209 This module provides functions that are the inverse of built-in perl
210 functions C<localtime()> and C<gmtime()>. They accept a date as a
211 six-element array, and return the corresponding C<time(2)> value in
212 seconds since the system epoch (Midnight, January 1, 1970 GMT on Unix,
213 for example). This value can be positive or negative, though POSIX
214 only requires support for positive values, so dates before the
215 system's epoch may not work on all operating systems.
217 It is worth drawing particular attention to the expected ranges for
218 the values provided. The value for the day of the month is the actual
219 day (ie 1..31), while the month is the number of months since January
220 (0..11). This is consistent with the values returned from
221 C<localtime()> and C<gmtime()>.
225 This module exports two functions by default, C<timelocal()> and
228 The C<timelocal()> and C<timegm()> functions perform range checking on
229 the input $sec, $min, $hour, $mday, and $mon values by default.
231 If you are working with data you know to be valid, you can speed your
232 code up by using the "nocheck" variants, C<timelocal_nocheck()> and
233 C<timegm_nocheck()>. These variants must be explicitly imported.
235 use Time::Local 'timelocal_nocheck';
237 # The 365th day of 1999
238 print scalar localtime timelocal_nocheck 0,0,0,365,0,99;
240 If you supply data which is not valid (month 27, second 1,000) the
241 results will be unpredictable (so don't do that).
243 =head2 Year Value Interpretation
245 Strictly speaking, the year should be specified in a form consistent
246 with C<localtime()>, i.e. the offset from 1900. In order to make the
247 interpretation of the year easier for humans, however, who are more
248 accustomed to seeing years as two-digit or four-digit values, the
249 following conventions are followed:
255 Years greater than 999 are interpreted as being the actual year,
256 rather than the offset from 1900. Thus, 1964 would indicate the year
257 Martin Luther King won the Nobel prize, not the year 3864.
261 Years in the range 100..999 are interpreted as offset from 1900, so
262 that 112 indicates 2012. This rule also applies to years less than
263 zero (but see note below regarding date range).
267 Years in the range 0..99 are interpreted as shorthand for years in the
268 rolling "current century," defined as 50 years on either side of the
269 current year. Thus, today, in 1999, 0 would refer to 2000, and 45 to
270 2045, but 55 would refer to 1955. Twenty years from now, 55 would
271 instead refer to 2055. This is messy, but matches the way people
272 currently think about two digit dates. Whenever possible, use an
273 absolute four digit year instead.
277 The scheme above allows interpretation of a wide range of dates,
278 particularly if 4-digit years are used.
280 =head2 Limits of time_t
282 The range of dates that can be actually be handled depends on the size
283 of C<time_t> (usually a signed integer) on the given
284 platform. Currently, this is 32 bits for most systems, yielding an
285 approximate range from Dec 1901 to Jan 2038.
287 Both C<timelocal()> and C<timegm()> croak if given dates outside the
290 =head2 Ambiguous Local Times (DST)
292 Because of DST changes, there are many time zones where the same local
293 time occurs for two different GMT times on the same day. For example,
294 in the "Europe/Paris" time zone, the local time of 2001-10-28 02:30:00
295 can represent either 2001-10-28 00:30:00 GMT, B<or> 2001-10-28
298 When given an ambiguous local time, the timelocal() function should
299 always return the epoch for the I<earlier> of the two possible GMT
302 =head2 Non-Existent Local Times (DST)
304 When a DST change causes a locale clock to skip one hour forward,
305 there will be an hour's worth of local times that don't exist. Again,
306 for the "Europe/Paris" time zone, the local clock jumped from
307 2001-03-25 01:59:59 to 2001-03-25 03:00:00.
309 If the C<timelocal()> function is given a non-existent local time, it
310 will simply return an epoch value for the time one hour later.
312 =head2 Negative Epoch Values
314 Negative epoch (C<time_t>) values are not officially supported by the
315 POSIX standards, so this module's tests do not test them. On some
316 systems, they are known not to work. These include MacOS (pre-OSX) and
319 On systems which do support negative epoch values, this module should
320 be able to cope with dates before the start of the epoch, down the
321 minimum value of time_t for the system.
323 =head1 IMPLEMENTATION
325 These routines are quite efficient and yet are always guaranteed to
326 agree with C<localtime()> and C<gmtime()>. We manage this by caching
327 the start times of any months we've seen before. If we know the start
328 time of the month, we can always calculate any time within the month.
329 The start times are calculated using a mathematical formula. Unlike
330 other algorithms that do multiple calls to C<gmtime()>.
332 The C<timelocal()> function is implemented using the same cache. We
333 just assume that we're translating a GMT time, and then fudge it when
334 we're done for the timezone and daylight savings arguments. Note that
335 the timezone is evaluated for each date because countries occasionally
336 change their official timezones. Assuming that C<localtime()> corrects
337 for these changes, this routine will also be correct.
341 The whole scheme for interpreting two-digit years can be considered a
346 Support for this module is provided via the datetime@perl.org email
347 list. See http://lists.perl.org/ for more details.
349 Please submit bugs to the CPAN RT system at
350 http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Time-Local or via email
351 at bug-time-local@rt.cpan.org.
355 This module is based on a Perl 4 library, timelocal.pl, that was
356 included with Perl 4.036, and was most likely written by Tom
359 The current version was written by Graham Barr.
361 It is now being maintained separately from the Perl core by Dave
362 Rolsky, <autarch@urth.org>.