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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 = '1.12_01'; |
11 | $VERSION = eval $VERSION; |
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 ); |
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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; |
24 | my $SecOff = 0; |
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25 | |
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26 | my ( %Options, %Cheat ); |
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27 | |
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28 | use constant SECS_PER_MINUTE => 60; |
29 | use constant SECS_PER_HOUR => 3600; |
30 | use constant SECS_PER_DAY => 86400; |
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31 | |
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32 | my $MaxInt = ( ( 1 << ( 8 * $Config{intsize} - 2 ) ) -1 ) * 2 + 1; |
33 | my $MaxDay = int( ( $MaxInt - ( SECS_PER_DAY / 2 ) ) / SECS_PER_DAY ) - 1; |
34 | |
35 | if ( $^O eq 'MacOS' ) { |
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36 | # time_t is unsigned... |
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37 | $MaxInt = ( 1 << ( 8 * $Config{intsize} ) ) - 1; |
38 | } |
39 | else { |
40 | $MaxInt = ( ( 1 << ( 8 * $Config{intsize} - 2 ) ) - 1 ) * 2 + 1; |
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41 | } |
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42 | |
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43 | # Determine the EPOC day for this machine |
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44 | my $Epoc = 0; |
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45 | if ( $^O eq 'vos' ) { |
46 | # work around posix-977 -- VOS doesn't handle dates in the range |
47 | # 1970-1980. |
48 | $Epoc = _daygm( 0, 0, 0, 1, 0, 70, 4, 0 ); |
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49 | } |
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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 |
54 | $Epoc = 693901; |
55 | $SecOff = timelocal( localtime(0)) - timelocal( gmtime(0) ) ; |
56 | $Epoc += _daygm( gmtime(0) ); |
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57 | } |
58 | else { |
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59 | $Epoc = _daygm( gmtime(0) ); |
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60 | } |
61 | |
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62 | %Cheat = (); # clear the cache as epoc has changed |
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63 | |
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64 | sub _daygm { |
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65 | |
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66 | # This is written in such a byzantine way in order to avoid |
67 | # lexical variables and sub calls, for speed |
68 | return $_[3] + ( |
69 | $Cheat{ pack( 'ss', @_[ 4, 5 ] ) } ||= do { |
70 | my $month = ( $_[4] + 10 ) % 12; |
71 | my $year = $_[5] + 1900 - $month / 10; |
72 | |
73 | ( ( 365 * $year ) |
74 | + ( $year / 4 ) |
75 | - ( $year / 100 ) |
76 | + ( $year / 400 ) |
77 | + ( ( ( $month * 306 ) + 5 ) / 10 ) |
78 | ) |
79 | - $Epoc; |
80 | } |
81 | ); |
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82 | } |
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83 | |
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84 | sub _timegm { |
85 | my $sec = |
86 | $SecOff + $_[0] + ( SECS_PER_MINUTE * $_[1] ) + ( SECS_PER_HOUR * $_[2] ); |
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87 | |
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88 | return $sec + ( SECS_PER_DAY * &_daygm ); |
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89 | } |
90 | |
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91 | sub timegm { |
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92 | my ( $sec, $min, $hour, $mday, $month, $year ) = @_; |
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93 | |
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94 | if ( $year >= 1000 ) { |
95 | $year -= 1900; |
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96 | } |
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97 | elsif ( $year < 100 and $year >= 0 ) { |
98 | $year += ( $year > $Breakpoint ) ? $Century : $NextCentury; |
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99 | } |
100 | |
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101 | unless ( $Options{no_range_check} ) { |
102 | if ( abs($year) >= 0x7fff ) { |
103 | $year += 1900; |
104 | croak |
105 | "Cannot handle date ($sec, $min, $hour, $mday, $month, *$year*)"; |
106 | } |
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107 | |
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108 | croak "Month '$month' out of range 0..11" |
109 | if $month > 11 |
110 | or $month < 0; |
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111 | |
112 | my $md = $MonthDays[$month]; |
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113 | ++$md |
114 | 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 | |
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122 | my $days = _daygm( undef, undef, undef, $mday, $month, $year ); |
123 | |
124 | unless ($Options{no_range_check} or abs($days) < $MaxDay) { |
125 | my $msg = ''; |
126 | $msg .= "Day too big - $days > $MaxDay\n" if $days > $MaxDay; |
127 | |
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128 | $year += 1900; |
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129 | $msg .= "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)"; |
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130 | |
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131 | croak $msg; |
132 | } |
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133 | |
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134 | return $sec |
135 | + $SecOff |
136 | + ( SECS_PER_MINUTE * $min ) |
137 | + ( SECS_PER_HOUR * $hour ) |
138 | + ( SECS_PER_DAY * $days ); |
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139 | } |
140 | |
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141 | sub timegm_nocheck { |
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142 | local $Options{no_range_check} = 1; |
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143 | return &timegm; |
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144 | } |
145 | |
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146 | sub timelocal { |
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147 | my $ref_t = &timegm; |
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148 | my $loc_t = _timegm( localtime($ref_t) ); |
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149 | |
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150 | # Is there a timezone offset from GMT or are we done? |
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151 | my $zone_off = $ref_t - $loc_t |
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152 | or return $loc_t; |
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153 | |
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154 | # This hack is needed to always pick the first matching time |
155 | # during a DST change when time would otherwise be ambiguous |
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156 | $zone_off -= SECS_PER_HOUR if $ref_t >= SECS_PER_HOUR; |
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157 | |
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158 | # Adjust for timezone |
159 | $loc_t = $ref_t + $zone_off; |
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160 | |
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161 | # Are we close to a DST change or are we done |
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162 | my $dst_off = $ref_t - _timegm( localtime($loc_t) ) |
163 | or return $loc_t; |
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164 | |
165 | # Adjust for DST change |
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166 | $loc_t += $dst_off; |
167 | |
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168 | return $loc_t if $dst_off >= 0; |
169 | |
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170 | # for a negative offset from GMT, and if the original date |
171 | # was a non-extent gap in a forward DST jump, we should |
172 | # now have the wrong answer - undo the DST adjust; |
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173 | my ( $s, $m, $h ) = localtime($loc_t); |
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174 | $loc_t -= $dst_off if $s != $_[0] || $m != $_[1] || $h != $_[2]; |
175 | |
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176 | return $loc_t; |
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177 | } |
178 | |
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179 | sub timelocal_nocheck { |
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180 | local $Options{no_range_check} = 1; |
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181 | return &timelocal; |
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182 | } |
183 | |
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184 | 1; |
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185 | |
186 | __END__ |
187 | |
188 | =head1 NAME |
189 | |
190 | Time::Local - efficiently compute time from local and GMT time |
191 | |
192 | =head1 SYNOPSIS |
193 | |
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194 | $time = timelocal($sec,$min,$hour,$mday,$mon,$year); |
195 | $time = timegm($sec,$min,$hour,$mday,$mon,$year); |
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196 | |
197 | =head1 DESCRIPTION |
198 | |
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199 | These routines are the inverse of built-in perl functions localtime() |
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200 | and gmtime(). They accept a date as a six-element array, and return |
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201 | the corresponding time(2) value in seconds since the system epoch |
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202 | (Midnight, January 1, 1970 GMT on Unix, for example). This value can |
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203 | be positive or negative, though POSIX only requires support for |
204 | positive values, so dates before the system's epoch may not work on |
205 | all operating systems. |
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206 | |
207 | It is worth drawing particular attention to the expected ranges for |
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208 | the values provided. The value for the day of the month is the actual |
209 | day (ie 1..31), while the month is the number of months since January |
210 | (0..11). This is consistent with the values returned from localtime() |
211 | and gmtime(). |
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212 | |
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213 | The timelocal() and timegm() functions perform range checking on the |
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214 | input $sec, $min, $hour, $mday, and $mon values by default. If you |
215 | are confident that your data is good, you can explicitly import the |
216 | timelocal_nocheck() and timegm_nocheck() functions, which may provide |
217 | a small performance improvement. |
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218 | |
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219 | use Time::Local 'timelocal_nocheck'; |
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220 | |
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221 | # The 365th day of 1999 |
222 | print scalar localtime timelocal_nocheck 0,0,0,365,0,99; |
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223 | |
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224 | Strictly speaking, the year should also be specified in a form |
225 | consistent with localtime(), i.e. the offset from 1900. In order to |
226 | make the interpretation of the year easier for humans, however, who |
227 | are more accustomed to seeing years as two-digit or four-digit values, |
228 | the following conventions are followed: |
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229 | |
230 | =over 4 |
231 | |
232 | =item * |
233 | |
234 | Years greater than 999 are interpreted as being the actual year, |
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235 | rather than the offset from 1900. Thus, 1964 would indicate the year |
236 | Martin Luther King won the Nobel prize, not the year 3864. |
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237 | |
238 | =item * |
239 | |
240 | Years in the range 100..999 are interpreted as offset from 1900, |
241 | so that 112 indicates 2012. This rule also applies to years less than zero |
242 | (but see note below regarding date range). |
243 | |
244 | =item * |
245 | |
246 | Years in the range 0..99 are interpreted as shorthand for years in the |
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247 | rolling "current century," defined as 50 years on either side of the |
248 | current year. Thus, today, in 1999, 0 would refer to 2000, and 45 to |
249 | 2045, but 55 would refer to 1955. Twenty years from now, 55 would |
250 | instead refer to 2055. This is messy, but matches the way people |
251 | currently think about two digit dates. Whenever possible, use an |
252 | absolute four digit year instead. |
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253 | |
254 | =back |
255 | |
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256 | The scheme above allows interpretation of a wide range of dates, |
257 | particularly if 4-digit years are used. |
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258 | |
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259 | Please note, however, that the range of dates that can be actually be |
260 | handled depends on the size of an integer (time_t) on a given |
261 | platform. Currently, this is 32 bits for most systems, yielding an |
262 | approximate range from Dec 1901 to Jan 2038. |
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263 | |
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264 | Both timelocal() and timegm() croak if given dates outside the |
265 | supported range. |
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266 | |
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267 | =head2 Ambiguous Local Times (DST) |
268 | |
269 | Because of DST changes, there are many time zones where the same local |
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270 | time occurs for two different GMT times on the same day. For example, |
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271 | in the "Europe/Paris" time zone, the local time of 2001-10-28 02:30:00 |
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272 | can represent either 2001-10-28 00:30:00 GMT, B<or> 2001-10-28 |
273 | 01:30:00 GMT. |
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274 | |
275 | When given an ambiguous local time, the timelocal() function should |
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276 | always return the epoch for the I<earlier> of the two possible GMT |
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277 | times. |
278 | |
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279 | =head2 Non-Existent Local Times (DST) |
280 | |
281 | When a DST change causes a locale clock to skip one hour forward, |
282 | there will be an hour's worth of local times that don't exist. Again, |
283 | for the "Europe/Paris" time zone, the local clock jumped from |
284 | 2001-03-25 01:59:59 to 2001-03-25 03:00:00. |
285 | |
286 | If the timelocal() function is given a non-existent local time, it |
287 | will simply return an epoch value for the time one hour later. |
288 | |
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289 | =head2 Negative Epoch Values |
290 | |
291 | Negative epoch (time_t) values are not officially supported by the |
292 | POSIX standards, so this module's tests do not test them. On some |
293 | systems, they are known not to work. These include MacOS (pre-OSX) |
294 | and Win32. |
295 | |
296 | On systems which do support negative epoch values, this module should |
297 | be able to cope with dates before the start of the epoch, down the |
298 | minimum value of time_t for the system. |
299 | |
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300 | =head1 IMPLEMENTATION |
301 | |
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302 | These routines are quite efficient and yet are always guaranteed to |
303 | agree with localtime() and gmtime(). We manage this by caching the |
304 | start times of any months we've seen before. If we know the start |
305 | time of the month, we can always calculate any time within the month. |
306 | The start times are calculated using a mathematical formula. Unlike |
307 | other algorithms that do multiple calls to gmtime(). |
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308 | |
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309 | timelocal() is implemented using the same cache. We just assume that |
310 | we're translating a GMT time, and then fudge it when we're done for |
311 | the timezone and daylight savings arguments. Note that the timezone |
312 | is evaluated for each date because countries occasionally change their |
313 | official timezones. Assuming that localtime() corrects for these |
314 | changes, this routine will also be correct. |
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315 | |
316 | =head1 BUGS |
317 | |
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318 | The whole scheme for interpreting two-digit years can be considered a |
319 | bug. |
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320 | |
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321 | =head1 SUPPORT |
322 | |
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323 | Support for this module is provided via the datetime@perl.org email |
324 | list. See http://lists.perl.org/ for more details. |
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325 | |
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326 | Please submit bugs using the RT system at rt.cpan.org, or as a last |
327 | resort, to the datetime@perl.org list. |
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328 | |
329 | =head1 AUTHOR |
330 | |
331 | This module is based on a Perl 4 library, timelocal.pl, that was |
332 | included with Perl 4.036, and was most likely written by Tom |
333 | Christiansen. |
334 | |
335 | The current version was written by Graham Barr. |
336 | |
337 | It is now being maintained separately from the Perl core by Dave |
338 | Rolsky, <autarch@urth.org>. |
339 | |
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340 | =cut |
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341 | |