9 use vars qw( $VERSION @ISA @EXPORT @EXPORT_OK );
11 $VERSION = eval $VERSION;
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 = $NextCentury - 100;
26 my (%Options, %Cheat, %Min, %Max);
27 my ($MinInt, $MaxInt);
30 # time_t is unsigned...
31 $MaxInt = (1 << (8 * $Config{intsize})) - 1;
34 $MaxInt = ((1 << (8 * $Config{intsize} - 2))-1)*2 + 1;
35 $MinInt = -$MaxInt - 1;
38 $Max{Day} = ($MaxInt >> 1) / 43200;
39 $Min{Day} = ($MinInt)? -($Max{Day}+1) : 0;
41 $Max{Sec} = $MaxInt - 86400 * $Max{Day};
42 $Min{Sec} = $MinInt - 86400 * $Min{Day};
44 # Determine the EPOC day for this machine
47 # work around posix-977 -- VOS doesn't handle dates in
48 # the range 1970-1980.
49 $Epoc = _daygm((0, 0, 0, 1, 0, 70, 4, 0));
51 elsif ($^O eq 'MacOS') {
54 # MacOS time() is seconds since 1 Jan 1904, localtime
55 # so we need to calculate an offset to apply later
57 $SecOff = timelocal(localtime(0)) - timelocal(gmtime(0));
58 $Epoc += _daygm(gmtime(0));
61 $Epoc = _daygm(gmtime(0));
64 %Cheat=(); # clear the cache as epoc has changed
67 $_[3] + ($Cheat{pack("ss",@_[4,5])} ||= do {
68 my $month = ($_[4] + 10) % 12;
69 my $year = $_[5] + 1900 - $month/10;
70 365*$year + $year/4 - $year/100 + $year/400 + ($month*306 + 5)/10 - $Epoc
76 my $sec = $SecOff + $_[0] + 60 * $_[1] + 3600 * $_[2];
80 $sec + 86400 * &_daygm;
85 my ($day, $sec, $time) = @_;
87 $sec = $sec + _timegm(localtime($time)) - $time;
88 if ($sec >= 86400) { $day++; $sec -= 86400; }
89 if ($sec < 0) { $day--; $sec += 86400; }
96 my ($sec,$min,$hour,$mday,$month,$year) = @_;
101 elsif ($year < 100 and $year >= 0) {
102 $year += ($year > $Breakpoint) ? $Century : $NextCentury;
105 unless ($Options{no_range_check}) {
106 if (abs($year) >= 0x7fff) {
108 croak "Cannot handle date ($sec, $min, $hour, $mday, $month, *$year*)";
111 croak "Month '$month' out of range 0..11" if $month > 11 or $month < 0;
113 my $md = $MonthDays[$month];
114 ++$md 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);
123 my $xsec = $sec + $SecOff + 60*$min + 3600*$hour;
125 unless ($Options{no_range_check}
126 or ($days > $Min{Day} or $days == $Min{Day} and $xsec >= $Min{Sec})
127 and ($days < $Max{Day} or $days == $Max{Day} and $xsec <= $Max{Sec}))
129 warn "Day too small - $days > $Min{Day}\n" if $days < $Min{Day};
130 warn "Day too big - $days > $Max{Day}\n" if $days > $Max{Day};
131 warn "Sec too small - $days < $Min{Sec}\n" if $days < $Min{Sec};
132 warn "Sec too big - $days > $Max{Sec}\n" if $days > $Max{Sec};
134 croak "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)";
139 $xsec + 86400 * $days;
144 local $Options{no_range_check} = 1;
150 # Adjust Max/Min allowed times to fit local time zone and call timegm
151 local ($Max{Day}, $Max{Sec}) = _zoneadjust($Max{Day}, $Max{Sec}, $MaxInt);
152 local ($Min{Day}, $Min{Sec}) = _zoneadjust($Min{Day}, $Min{Sec}, $MinInt);
155 # Calculate first guess with a one-day delta to avoid localtime overflow
156 my $delta = ($_[5] < 100)? 86400 : -86400;
157 my $loc_t = _timegm(localtime( $ref_t + $delta )) - $delta;
159 # Is there a timezone offset from GMT or are we done
160 my $zone_off = $ref_t - $loc_t
163 # This hack is needed to always pick the first matching time
164 # during a DST change when time would otherwise be ambiguous
165 $zone_off -= 3600 if ($delta > 0 && $ref_t >= 3600);
167 # Adjust for timezone
168 $loc_t = $ref_t + $zone_off;
170 # Are we close to a DST change or are we done
171 my $dst_off = $ref_t - _timegm(localtime($loc_t))
174 # Adjust for DST change
177 return $loc_t if $dst_off >= 0;
179 # for a negative offset from GMT, and if the original date
180 # was a non-extent gap in a forward DST jump, we should
181 # now have the wrong answer - undo the DST adjust;
183 my ($s,$m,$h) = localtime($loc_t);
184 $loc_t -= $dst_off if $s != $_[0] || $m != $_[1] || $h != $_[2];
190 sub timelocal_nocheck {
191 local $Options{no_range_check} = 1;
201 Time::Local - efficiently compute time from local and GMT time
205 $time = timelocal($sec,$min,$hour,$mday,$mon,$year);
206 $time = timegm($sec,$min,$hour,$mday,$mon,$year);
210 These routines are the inverse of built-in perl functions localtime()
211 and gmtime(). They accept a date as a six-element array, and return
212 the corresponding time(2) value in seconds since the system epoch
213 (Midnight, January 1, 1970 GMT on Unix, for example). This value can
214 be positive or negative, though POSIX only requires support for
215 positive values, so dates before the system's epoch may not work on
216 all operating systems.
218 It is worth drawing particular attention to the expected ranges for
219 the values provided. The value for the day of the month is the actual day
220 (ie 1..31), while the month is the number of months since January (0..11).
221 This is consistent with the values returned from localtime() and gmtime().
223 The timelocal() and timegm() functions perform range checking on the
224 input $sec, $min, $hour, $mday, and $mon values by default. If you'd
225 rather they didn't, you can explicitly import the timelocal_nocheck()
226 and timegm_nocheck() functions.
228 use Time::Local 'timelocal_nocheck';
231 # The 365th day of 1999
232 print scalar localtime timelocal_nocheck 0,0,0,365,0,99;
234 # The twenty thousandth day since 1970
235 print scalar localtime timelocal_nocheck 0,0,0,20000,0,70;
237 # And even the 10,000,000th second since 1999!
238 print scalar localtime timelocal_nocheck 10000000,0,0,1,0,99;
241 Your mileage may vary when trying these with minutes and hours,
242 and it doesn't work at all for months.
244 Strictly speaking, the year should also be specified in a form consistent
245 with localtime(), i.e. the offset from 1900.
246 In order to make the interpretation of the year easier for humans,
247 however, who are more accustomed to seeing years as two-digit or four-digit
248 values, the following conventions are followed:
254 Years greater than 999 are interpreted as being the actual year,
255 rather than the offset from 1900. Thus, 1963 would indicate the year
256 Martin Luther King won the Nobel prize, not the year 3863.
260 Years in the range 100..999 are interpreted as offset from 1900,
261 so that 112 indicates 2012. This rule also applies to years less than zero
262 (but see note below regarding date range).
266 Years in the range 0..99 are interpreted as shorthand for years in the
267 rolling "current century," defined as 50 years on either side of the current
268 year. Thus, today, in 1999, 0 would refer to 2000, and 45 to 2045,
269 but 55 would refer to 1955. Twenty years from now, 55 would instead refer
270 to 2055. This is messy, but matches the way people currently think about
271 two digit dates. Whenever possible, use an absolute four digit year instead.
275 The scheme above allows interpretation of a wide range of dates, particularly
276 if 4-digit years are used.
278 Please note, however, that the range of dates that can be actually be handled
279 depends on the size of an integer (time_t) on a given platform.
280 Currently, this is 32 bits for most systems, yielding an approximate range
281 from Dec 1901 to Jan 2038.
283 Both timelocal() and timegm() croak if given dates outside the supported
286 =head2 Ambiguous Local Times (DST)
288 Because of DST changes, there are many time zones where the same local
289 time occurs for two different GMT times on the same day. For example,
290 in the "Europe/Paris" time zone, the local time of 2001-10-28 02:30:00
291 can represent either 2001-10-28 00:30:00 GMT, B<or> 2001-10-28
294 When given an ambiguous local time, the timelocal() function should
295 always return the epoch for the I<earlier> of the two possible GMT
298 =head2 Non-Existent Local Times (DST)
300 When a DST change causes a locale clock to skip one hour forward,
301 there will be an hour's worth of local times that don't exist. Again,
302 for the "Europe/Paris" time zone, the local clock jumped from
303 2001-03-25 01:59:59 to 2001-03-25 03:00:00.
305 If the timelocal() function is given a non-existent local time, it
306 will simply return an epoch value for the time one hour later.
308 =head2 Negative Epoch Values
310 Negative epoch (time_t) values are not officially supported by the
311 POSIX standards, so this module's tests do not test them. On some
312 systems, they are known not to work. These include MacOS (pre-OSX)
315 On systems which do support negative epoch values, this module should
316 be able to cope with dates before the start of the epoch, down the
317 minimum value of time_t for the system.
319 =head1 IMPLEMENTATION
321 These routines are quite efficient and yet are always guaranteed to agree
322 with localtime() and gmtime(). We manage this by caching the start times
323 of any months we've seen before. If we know the start time of the month,
324 we can always calculate any time within the month. The start times
325 are calculated using a mathematical formula. Unlike other algorithms
326 that do multiple calls to gmtime().
328 timelocal() is implemented using the same cache. We just assume that we're
329 translating a GMT time, and then fudge it when we're done for the timezone
330 and daylight savings arguments. Note that the timezone is evaluated for
331 each date because countries occasionally change their official timezones.
332 Assuming that localtime() corrects for these changes, this routine will
337 The whole scheme for interpreting two-digit years can be considered a bug.
341 Support for this module is provided via the datetime@perl.org
342 email list. See http://lists.perl.org/ for more details.
344 Please submit bugs using the RT system at rt.cpan.org, or as a last
345 resort, to the datetime@perl.org list.
349 This module is based on a Perl 4 library, timelocal.pl, that was
350 included with Perl 4.036, and was most likely written by Tom
353 The current version was written by Graham Barr.
355 It is now being maintained separately from the Perl core by Dave
356 Rolsky, <autarch@urth.org>.