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1 | package Time::Local; |
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2 | |
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3 | require Exporter; |
4 | use Carp; |
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5 | use Config; |
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6 | use strict; |
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7 | use integer; |
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8 | |
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9 | use vars qw( $VERSION @ISA @EXPORT @EXPORT_OK ); |
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10 | $VERSION = '1.10'; |
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11 | $VERSION = eval $VERSION; |
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12 | @ISA = qw( Exporter ); |
13 | @EXPORT = qw( timegm timelocal ); |
14 | @EXPORT_OK = qw( timegm_nocheck timelocal_nocheck ); |
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15 | |
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16 | my @MonthDays = (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31); |
17 | |
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18 | # Determine breakpoint for rolling century |
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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; |
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24 | my $SecOff = 0; |
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25 | |
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26 | my (%Options, %Cheat, %Min, %Max); |
27 | my ($MinInt, $MaxInt); |
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28 | |
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29 | if ($^O eq 'MacOS') { |
30 | # time_t is unsigned... |
31 | $MaxInt = (1 << (8 * $Config{intsize})) - 1; |
32 | $MinInt = 0; |
33 | } else { |
34 | $MaxInt = ((1 << (8 * $Config{intsize} - 2))-1)*2 + 1; |
35 | $MinInt = -$MaxInt - 1; |
36 | } |
37 | |
38 | $Max{Day} = ($MaxInt >> 1) / 43200; |
39 | $Min{Day} = ($MinInt)? -($Max{Day}+1) : 0; |
40 | |
41 | $Max{Sec} = $MaxInt - 86400 * $Max{Day}; |
42 | $Min{Sec} = $MinInt - 86400 * $Min{Day}; |
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43 | |
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44 | # Determine the EPOC day for this machine |
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45 | my $Epoc = 0; |
46 | if ($^O eq 'vos') { |
47 | # work around posix-977 -- VOS doesn't handle dates in |
48 | # the range 1970-1980. |
49 | $Epoc = _daygm((0, 0, 0, 1, 0, 70, 4, 0)); |
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50 | } |
51 | elsif ($^O eq 'MacOS') { |
52 | no integer; |
53 | |
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54 | # MacOS time() is seconds since 1 Jan 1904, localtime |
55 | # so we need to calculate an offset to apply later |
56 | $Epoc = 693901; |
57 | $SecOff = timelocal(localtime(0)) - timelocal(gmtime(0)); |
58 | $Epoc += _daygm(gmtime(0)); |
59 | } |
60 | else { |
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61 | $Epoc = _daygm(gmtime(0)); |
62 | } |
63 | |
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64 | %Cheat=(); # clear the cache as epoc has changed |
65 | |
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66 | sub _daygm { |
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 |
71 | }); |
72 | } |
73 | |
74 | |
75 | sub _timegm { |
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76 | my $sec = $SecOff + $_[0] + 60 * $_[1] + 3600 * $_[2]; |
77 | |
78 | no integer; |
79 | |
80 | $sec + 86400 * &_daygm; |
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81 | } |
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82 | |
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83 | |
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84 | sub _zoneadjust { |
85 | my ($day, $sec, $time) = @_; |
86 | |
87 | $sec = $sec + _timegm(localtime($time)) - $time; |
88 | if ($sec >= 86400) { $day++; $sec -= 86400; } |
89 | if ($sec < 0) { $day--; $sec += 86400; } |
90 | |
91 | ($day, $sec); |
92 | } |
93 | |
94 | |
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95 | sub timegm { |
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96 | my ($sec,$min,$hour,$mday,$month,$year) = @_; |
97 | |
98 | if ($year >= 1000) { |
99 | $year -= 1900; |
100 | } |
101 | elsif ($year < 100 and $year >= 0) { |
102 | $year += ($year > $Breakpoint) ? $Century : $NextCentury; |
103 | } |
104 | |
105 | unless ($Options{no_range_check}) { |
106 | if (abs($year) >= 0x7fff) { |
107 | $year += 1900; |
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108 | croak "Cannot handle date ($sec, $min, $hour, $mday, $month, *$year*)"; |
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109 | } |
110 | |
111 | croak "Month '$month' out of range 0..11" if $month > 11 or $month < 0; |
112 | |
113 | my $md = $MonthDays[$month]; |
114 | ++$md unless $month != 1 or $year % 4 or !($year % 400); |
115 | |
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; |
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120 | } |
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121 | |
122 | my $days = _daygm(undef, undef, undef, $mday, $month, $year); |
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123 | my $xsec = $sec + $SecOff + 60*$min + 3600*$hour; |
124 | |
125 | unless ($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})) |
128 | { |
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}; |
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133 | $year += 1900; |
134 | croak "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)"; |
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135 | } |
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136 | |
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137 | no integer; |
138 | |
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139 | $xsec + 86400 * $days; |
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140 | } |
141 | |
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142 | |
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143 | sub timegm_nocheck { |
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144 | local $Options{no_range_check} = 1; |
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145 | &timegm; |
146 | } |
147 | |
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148 | |
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149 | sub timelocal { |
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150 | # Adjust Max/Min allowed times to fit local time zone and call timegm |
151 | local ($Max{Day}, $Max{Sec}) = _zoneadjust($Max{Day}, $Max{Sec}, $MaxInt); |
152 | local ($Min{Day}, $Min{Sec}) = _zoneadjust($Min{Day}, $Min{Sec}, $MinInt); |
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153 | my $ref_t = &timegm; |
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154 | |
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; |
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158 | |
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159 | # Is there a timezone offset from GMT or are we done |
160 | my $zone_off = $ref_t - $loc_t |
161 | or return $loc_t; |
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162 | |
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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); |
166 | |
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167 | # Adjust for timezone |
168 | $loc_t = $ref_t + $zone_off; |
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169 | |
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170 | # Are we close to a DST change or are we done |
171 | my $dst_off = $ref_t - _timegm(localtime($loc_t)) |
172 | or return $loc_t; |
173 | |
174 | # Adjust for DST change |
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175 | $loc_t += $dst_off; |
176 | |
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177 | return $loc_t if $dst_off >= 0; |
178 | |
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179 | # for a negative offset from GMT, and if the original date |
180 | # was a non-extent gap in a forward DST jump, we should |
181 | # now have the wrong answer - undo the DST adjust; |
182 | |
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183 | my ($s,$m,$h) = localtime($loc_t); |
184 | $loc_t -= $dst_off if $s != $_[0] || $m != $_[1] || $h != $_[2]; |
185 | |
186 | $loc_t; |
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187 | } |
188 | |
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189 | |
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190 | sub timelocal_nocheck { |
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191 | local $Options{no_range_check} = 1; |
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192 | &timelocal; |
193 | } |
194 | |
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195 | 1; |
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196 | |
197 | __END__ |
198 | |
199 | =head1 NAME |
200 | |
201 | Time::Local - efficiently compute time from local and GMT time |
202 | |
203 | =head1 SYNOPSIS |
204 | |
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205 | $time = timelocal($sec,$min,$hour,$mday,$mon,$year); |
206 | $time = timegm($sec,$min,$hour,$mday,$mon,$year); |
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207 | |
208 | =head1 DESCRIPTION |
209 | |
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210 | These routines are the inverse of built-in perl functions localtime() |
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211 | and gmtime(). They accept a date as a six-element array, and return |
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212 | the corresponding time(2) value in seconds since the system epoch |
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213 | (Midnight, January 1, 1970 GMT on Unix, for example). This value can |
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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. |
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217 | |
218 | It is worth drawing particular attention to the expected ranges for |
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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). |
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221 | This is consistent with the values returned from localtime() and gmtime(). |
222 | |
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223 | The timelocal() and timegm() functions perform range checking on the |
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224 | input $sec, $min, $hour, $mday, and $mon values by default. If you'd |
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225 | rather they didn't, you can explicitly import the timelocal_nocheck() |
226 | and timegm_nocheck() functions. |
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227 | |
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228 | use Time::Local 'timelocal_nocheck'; |
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229 | |
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230 | { |
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231 | # The 365th day of 1999 |
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232 | print scalar localtime timelocal_nocheck 0,0,0,365,0,99; |
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233 | |
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234 | # The twenty thousandth day since 1970 |
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235 | print scalar localtime timelocal_nocheck 0,0,0,20000,0,70; |
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236 | |
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237 | # And even the 10,000,000th second since 1999! |
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238 | print scalar localtime timelocal_nocheck 10000000,0,0,1,0,99; |
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239 | } |
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240 | |
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241 | Your mileage may vary when trying these with minutes and hours, |
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242 | and it doesn't work at all for months. |
243 | |
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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: |
249 | |
250 | =over 4 |
251 | |
252 | =item * |
253 | |
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 |
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256 | Martin Luther King won the Nobel prize, not the year 3863. |
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257 | |
258 | =item * |
259 | |
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). |
263 | |
264 | =item * |
265 | |
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. |
272 | |
273 | =back |
274 | |
275 | The scheme above allows interpretation of a wide range of dates, particularly |
276 | if 4-digit years are used. |
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277 | |
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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. |
282 | |
283 | Both timelocal() and timegm() croak if given dates outside the supported |
284 | range. |
285 | |
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286 | =head2 Ambiguous Local Times (DST) |
287 | |
288 | Because of DST changes, there are many time zones where the same local |
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289 | time occurs for two different GMT times on the same day. For example, |
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290 | in the "Europe/Paris" time zone, the local time of 2001-10-28 02:30:00 |
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291 | can represent either 2001-10-28 00:30:00 GMT, B<or> 2001-10-28 |
292 | 01:30:00 GMT. |
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293 | |
294 | When given an ambiguous local time, the timelocal() function should |
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295 | always return the epoch for the I<earlier> of the two possible GMT |
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296 | times. |
297 | |
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298 | =head2 Non-Existent Local Times (DST) |
299 | |
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. |
304 | |
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. |
307 | |
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308 | =head2 Negative Epoch Values |
309 | |
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) |
313 | and Win32. |
314 | |
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. |
318 | |
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319 | =head1 IMPLEMENTATION |
320 | |
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 |
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325 | are calculated using a mathematical formula. Unlike other algorithms |
326 | that do multiple calls to gmtime(). |
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327 | |
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 |
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333 | also be correct. |
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334 | |
335 | =head1 BUGS |
336 | |
337 | The whole scheme for interpreting two-digit years can be considered a bug. |
338 | |
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339 | =head1 SUPPORT |
340 | |
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341 | Support for this module is provided via the datetime@perl.org |
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342 | email list. See http://lists.perl.org/ for more details. |
343 | |
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344 | Please submit bugs using the RT system at rt.cpan.org, or as a last |
345 | resort, to the datetime@perl.org list. |
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346 | |
347 | =head1 AUTHOR |
348 | |
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 |
351 | Christiansen. |
352 | |
353 | The current version was written by Graham Barr. |
354 | |
355 | It is now being maintained separately from the Perl core by Dave |
356 | Rolsky, <autarch@urth.org>. |
357 | |
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358 | =cut |
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359 | |