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 unless $month != 1 or $year % 4 or !( $year % 400 );
116 croak "Day '$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 local $Options{no_range_check} = 1;
148 my $loc_for_ref_t = _timegm( localtime($ref_t) );
150 my $zone_off = $loc_for_ref_t - $ref_t
151 or return $loc_for_ref_t;
153 # Adjust for timezone
154 my $loc_t = $ref_t - $zone_off;
156 # Are we close to a DST change or are we done
157 my $dst_off = $ref_t - _timegm( localtime($loc_t) );
159 # If this evaluates to true, it means that the value in $loc_t is
160 # the _second_ hour after a DST change where the local time moves
163 ( ( $ref_t - SECS_PER_HOUR ) - _timegm( localtime( $loc_t - SECS_PER_HOUR ) ) < 0 )
165 return $loc_t - SECS_PER_HOUR;
168 # Adjust for DST change
171 return $loc_t if $dst_off > 0;
173 # If the original date was a non-extent gap in a forward DST jump,
174 # we should now have the wrong answer - undo the DST adjustment
175 my ( $s, $m, $h ) = localtime($loc_t);
176 $loc_t -= $dst_off if $s != $_[0] || $m != $_[1] || $h != $_[2];
181 sub timelocal_nocheck {
182 local $Options{no_range_check} = 1;
192 Time::Local - efficiently compute time from local and GMT time
196 $time = timelocal($sec,$min,$hour,$mday,$mon,$year);
197 $time = timegm($sec,$min,$hour,$mday,$mon,$year);
201 This module provides functions that are the inverse of built-in perl
202 functions C<localtime()> and C<gmtime()>. They accept a date as a
203 six-element array, and return the corresponding C<time(2)> value in
204 seconds since the system epoch (Midnight, January 1, 1970 GMT on Unix,
205 for example). This value can be positive or negative, though POSIX
206 only requires support for positive values, so dates before the
207 system's epoch may not work on all operating systems.
209 It is worth drawing particular attention to the expected ranges for
210 the values provided. The value for the day of the month is the actual
211 day (ie 1..31), while the month is the number of months since January
212 (0..11). This is consistent with the values returned from
213 C<localtime()> and C<gmtime()>.
217 This module exports two functions by default, C<timelocal()> and
220 The C<timelocal()> and C<timegm()> functions perform range checking on
221 the input $sec, $min, $hour, $mday, and $mon values by default.
223 If you are working with data you know to be valid, you can speed your
224 code up by using the "nocheck" variants, C<timelocal_nocheck()> and
225 C<timegm_nocheck()>. These variants must be explicitly imported.
227 use Time::Local 'timelocal_nocheck';
229 # The 365th day of 1999
230 print scalar localtime timelocal_nocheck 0,0,0,365,0,99;
232 If you supply data which is not valid (month 27, second 1,000) the
233 results will be unpredictable (so don't do that).
235 =head2 Year Value Interpretation
237 Strictly speaking, the year should be specified in a form consistent
238 with C<localtime()>, i.e. the offset from 1900. In order to make the
239 interpretation of the year easier for humans, however, who are more
240 accustomed to seeing years as two-digit or four-digit values, the
241 following conventions are followed:
247 Years greater than 999 are interpreted as being the actual year,
248 rather than the offset from 1900. Thus, 1964 would indicate the year
249 Martin Luther King won the Nobel prize, not the year 3864.
253 Years in the range 100..999 are interpreted as offset from 1900, so
254 that 112 indicates 2012. This rule also applies to years less than
255 zero (but see note below regarding date range).
259 Years in the range 0..99 are interpreted as shorthand for years in the
260 rolling "current century," defined as 50 years on either side of the
261 current year. Thus, today, in 1999, 0 would refer to 2000, and 45 to
262 2045, but 55 would refer to 1955. Twenty years from now, 55 would
263 instead refer to 2055. This is messy, but matches the way people
264 currently think about two digit dates. Whenever possible, use an
265 absolute four digit year instead.
269 The scheme above allows interpretation of a wide range of dates,
270 particularly if 4-digit years are used.
272 =head2 Limits of time_t
274 The range of dates that can be actually be handled depends on the size
275 of C<time_t> (usually a signed integer) on the given
276 platform. Currently, this is 32 bits for most systems, yielding an
277 approximate range from Dec 1901 to Jan 2038.
279 Both C<timelocal()> and C<timegm()> croak if given dates outside the
282 =head2 Ambiguous Local Times (DST)
284 Because of DST changes, there are many time zones where the same local
285 time occurs for two different GMT times on the same day. For example,
286 in the "Europe/Paris" time zone, the local time of 2001-10-28 02:30:00
287 can represent either 2001-10-28 00:30:00 GMT, B<or> 2001-10-28
290 When given an ambiguous local time, the timelocal() function should
291 always return the epoch for the I<earlier> of the two possible GMT
294 =head2 Non-Existent Local Times (DST)
296 When a DST change causes a locale clock to skip one hour forward,
297 there will be an hour's worth of local times that don't exist. Again,
298 for the "Europe/Paris" time zone, the local clock jumped from
299 2001-03-25 01:59:59 to 2001-03-25 03:00:00.
301 If the C<timelocal()> function is given a non-existent local time, it
302 will simply return an epoch value for the time one hour later.
304 =head2 Negative Epoch Values
306 Negative epoch (C<time_t>) values are not officially supported by the
307 POSIX standards, so this module's tests do not test them. On some
308 systems, they are known not to work. These include MacOS (pre-OSX) and
311 On systems which do support negative epoch values, this module should
312 be able to cope with dates before the start of the epoch, down the
313 minimum value of time_t for the system.
315 =head1 IMPLEMENTATION
317 These routines are quite efficient and yet are always guaranteed to
318 agree with C<localtime()> and C<gmtime()>. We manage this by caching
319 the start times of any months we've seen before. If we know the start
320 time of the month, we can always calculate any time within the month.
321 The start times are calculated using a mathematical formula. Unlike
322 other algorithms that do multiple calls to C<gmtime()>.
324 The C<timelocal()> function is implemented using the same cache. We
325 just assume that we're translating a GMT time, and then fudge it when
326 we're done for the timezone and daylight savings arguments. Note that
327 the timezone is evaluated for each date because countries occasionally
328 change their official timezones. Assuming that C<localtime()> corrects
329 for these changes, this routine will also be correct.
333 The whole scheme for interpreting two-digit years can be considered a
338 Support for this module is provided via the datetime@perl.org email
339 list. See http://lists.perl.org/ for more details.
341 Please submit bugs to the CPAN RT system at
342 http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Time-Local or via email
343 at bug-time-local@rt.cpan.org.
347 This module is based on a Perl 4 library, timelocal.pl, that was
348 included with Perl 4.036, and was most likely written by Tom
351 The current version was written by Graham Barr.
353 It is now being maintained separately from the Perl core by Dave
354 Rolsky, <autarch@urth.org>.