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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 = '1.15'; |
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11 | |
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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 ); |
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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 | # Need to check leap year before altering the value |
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95 | my $leap_year = _is_leap_year($year); |
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96 | |
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97 | if ( $year >= 1000 ) { |
98 | $year -= 1900; |
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99 | } |
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100 | elsif ( $year < 100 and $year >= 0 ) { |
101 | $year += ( $year > $Breakpoint ) ? $Century : $NextCentury; |
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102 | } |
103 | |
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104 | unless ( $Options{no_range_check} ) { |
105 | if ( abs($year) >= 0x7fff ) { |
106 | $year += 1900; |
107 | croak |
108 | "Cannot handle date ($sec, $min, $hour, $mday, $month, *$year*)"; |
109 | } |
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110 | |
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111 | croak "Month '$month' out of range 0..11" |
112 | if $month > 11 |
113 | or $month < 0; |
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114 | |
115 | my $md = $MonthDays[$month]; |
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116 | ++$md |
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117 | if $month == 1 && $leap_year; |
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118 | |
119 | croak "Day '$mday' out of range 1..$md" if $mday > $md or $mday < 1; |
120 | croak "Hour '$hour' out of range 0..23" if $hour > 23 or $hour < 0; |
121 | croak "Minute '$min' out of range 0..59" if $min > 59 or $min < 0; |
122 | croak "Second '$sec' out of range 0..59" if $sec > 59 or $sec < 0; |
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123 | } |
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124 | |
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125 | my $days = _daygm( undef, undef, undef, $mday, $month, $year ); |
126 | |
127 | unless ($Options{no_range_check} or abs($days) < $MaxDay) { |
128 | my $msg = ''; |
129 | $msg .= "Day too big - $days > $MaxDay\n" if $days > $MaxDay; |
130 | |
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131 | $year += 1900; |
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132 | $msg .= "Cannot handle date ($sec, $min, $hour, $mday, $month, $year)"; |
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133 | |
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134 | croak $msg; |
135 | } |
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136 | |
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137 | return $sec |
138 | + $SecOff |
139 | + ( SECS_PER_MINUTE * $min ) |
140 | + ( SECS_PER_HOUR * $hour ) |
141 | + ( SECS_PER_DAY * $days ); |
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142 | } |
143 | |
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144 | sub _is_leap_year { |
145 | return 0 if $_[0] % 4; |
146 | return 1 if $_[0] % 100; |
147 | return 0 if $_[0] % 400; |
148 | |
149 | return 1; |
150 | } |
151 | |
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152 | sub timegm_nocheck { |
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153 | local $Options{no_range_check} = 1; |
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154 | return &timegm; |
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155 | } |
156 | |
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157 | sub timelocal { |
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158 | my $ref_t = &timegm; |
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159 | my $loc_for_ref_t = _timegm( localtime($ref_t) ); |
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160 | |
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161 | my $zone_off = $loc_for_ref_t - $ref_t |
162 | or return $loc_for_ref_t; |
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163 | |
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164 | # Adjust for timezone |
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165 | my $loc_t = $ref_t - $zone_off; |
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166 | |
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167 | # Are we close to a DST change or are we done |
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168 | my $dst_off = $ref_t - _timegm( localtime($loc_t) ); |
169 | |
170 | # If this evaluates to true, it means that the value in $loc_t is |
171 | # the _second_ hour after a DST change where the local time moves |
172 | # backward. |
173 | if ( ! $dst_off && |
174 | ( ( $ref_t - SECS_PER_HOUR ) - _timegm( localtime( $loc_t - SECS_PER_HOUR ) ) < 0 ) |
175 | ) { |
176 | return $loc_t - SECS_PER_HOUR; |
177 | } |
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178 | |
179 | # Adjust for DST change |
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180 | $loc_t += $dst_off; |
181 | |
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182 | return $loc_t if $dst_off > 0; |
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183 | |
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184 | # If the original date was a non-extent gap in a forward DST jump, |
185 | # we should now have the wrong answer - undo the DST adjustment |
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186 | my ( $s, $m, $h ) = localtime($loc_t); |
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187 | $loc_t -= $dst_off if $s != $_[0] || $m != $_[1] || $h != $_[2]; |
188 | |
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189 | return $loc_t; |
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190 | } |
191 | |
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192 | sub timelocal_nocheck { |
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193 | local $Options{no_range_check} = 1; |
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194 | return &timelocal; |
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195 | } |
196 | |
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197 | 1; |
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198 | |
199 | __END__ |
200 | |
201 | =head1 NAME |
202 | |
203 | Time::Local - efficiently compute time from local and GMT time |
204 | |
205 | =head1 SYNOPSIS |
206 | |
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207 | $time = timelocal($sec,$min,$hour,$mday,$mon,$year); |
208 | $time = timegm($sec,$min,$hour,$mday,$mon,$year); |
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209 | |
210 | =head1 DESCRIPTION |
211 | |
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212 | This module provides functions that are the inverse of built-in perl |
213 | functions C<localtime()> and C<gmtime()>. They accept a date as a |
214 | six-element array, and return the corresponding C<time(2)> value in |
215 | seconds since the system epoch (Midnight, January 1, 1970 GMT on Unix, |
216 | for example). This value can be positive or negative, though POSIX |
217 | only requires support for positive values, so dates before the |
218 | system's epoch may not work on all operating systems. |
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219 | |
220 | It is worth drawing particular attention to the expected ranges for |
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221 | the values provided. The value for the day of the month is the actual |
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222 | day (ie 1..31), while the month is the number of months since January |
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223 | (0..11). This is consistent with the values returned from |
224 | C<localtime()> and C<gmtime()>. |
225 | |
226 | =head1 FUNCTIONS |
227 | |
228 | This module exports two functions by default, C<timelocal()> and |
229 | C<timegm()>. |
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230 | |
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231 | The C<timelocal()> and C<timegm()> functions perform range checking on |
232 | the input $sec, $min, $hour, $mday, and $mon values by default. |
233 | |
234 | If you are working with data you know to be valid, you can speed your |
235 | code up by using the "nocheck" variants, C<timelocal_nocheck()> and |
236 | C<timegm_nocheck()>. These variants must be explicitly imported. |
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237 | |
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238 | use Time::Local 'timelocal_nocheck'; |
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239 | |
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240 | # The 365th day of 1999 |
241 | print scalar localtime timelocal_nocheck 0,0,0,365,0,99; |
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242 | |
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243 | If you supply data which is not valid (month 27, second 1,000) the |
244 | results will be unpredictable (so don't do that). |
245 | |
246 | =head2 Year Value Interpretation |
247 | |
248 | Strictly speaking, the year should be specified in a form consistent |
249 | with C<localtime()>, i.e. the offset from 1900. In order to make the |
250 | interpretation of the year easier for humans, however, who are more |
251 | accustomed to seeing years as two-digit or four-digit values, the |
252 | following conventions are followed: |
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253 | |
254 | =over 4 |
255 | |
256 | =item * |
257 | |
258 | Years greater than 999 are interpreted as being the actual year, |
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259 | rather than the offset from 1900. Thus, 1964 would indicate the year |
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260 | Martin Luther King won the Nobel prize, not the year 3864. |
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261 | |
262 | =item * |
263 | |
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264 | Years in the range 100..999 are interpreted as offset from 1900, so |
265 | that 112 indicates 2012. This rule also applies to years less than |
266 | zero (but see note below regarding date range). |
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267 | |
268 | =item * |
269 | |
270 | Years in the range 0..99 are interpreted as shorthand for years in the |
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271 | rolling "current century," defined as 50 years on either side of the |
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272 | current year. Thus, today, in 1999, 0 would refer to 2000, and 45 to |
273 | 2045, but 55 would refer to 1955. Twenty years from now, 55 would |
274 | instead refer to 2055. This is messy, but matches the way people |
275 | currently think about two digit dates. Whenever possible, use an |
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276 | absolute four digit year instead. |
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277 | |
278 | =back |
279 | |
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280 | The scheme above allows interpretation of a wide range of dates, |
281 | particularly if 4-digit years are used. |
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282 | |
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283 | =head2 Limits of time_t |
284 | |
285 | The range of dates that can be actually be handled depends on the size |
286 | of C<time_t> (usually a signed integer) on the given |
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287 | platform. Currently, this is 32 bits for most systems, yielding an |
288 | approximate range from Dec 1901 to Jan 2038. |
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289 | |
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290 | Both C<timelocal()> and C<timegm()> croak if given dates outside the |
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291 | supported range. |
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292 | |
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293 | =head2 Ambiguous Local Times (DST) |
294 | |
295 | Because of DST changes, there are many time zones where the same local |
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296 | time occurs for two different GMT times on the same day. For example, |
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297 | in the "Europe/Paris" time zone, the local time of 2001-10-28 02:30:00 |
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298 | can represent either 2001-10-28 00:30:00 GMT, B<or> 2001-10-28 |
299 | 01:30:00 GMT. |
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300 | |
301 | When given an ambiguous local time, the timelocal() function should |
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302 | always return the epoch for the I<earlier> of the two possible GMT |
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303 | times. |
304 | |
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305 | =head2 Non-Existent Local Times (DST) |
306 | |
307 | When a DST change causes a locale clock to skip one hour forward, |
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308 | there will be an hour's worth of local times that don't exist. Again, |
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309 | for the "Europe/Paris" time zone, the local clock jumped from |
310 | 2001-03-25 01:59:59 to 2001-03-25 03:00:00. |
311 | |
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312 | If the C<timelocal()> function is given a non-existent local time, it |
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313 | will simply return an epoch value for the time one hour later. |
314 | |
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315 | =head2 Negative Epoch Values |
316 | |
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317 | Negative epoch (C<time_t>) values are not officially supported by the |
318 | POSIX standards, so this module's tests do not test them. On some |
319 | systems, they are known not to work. These include MacOS (pre-OSX) and |
320 | Win32. |
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321 | |
322 | On systems which do support negative epoch values, this module should |
323 | be able to cope with dates before the start of the epoch, down the |
324 | minimum value of time_t for the system. |
325 | |
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326 | =head1 IMPLEMENTATION |
327 | |
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328 | These routines are quite efficient and yet are always guaranteed to |
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329 | agree with C<localtime()> and C<gmtime()>. We manage this by caching |
330 | the start times of any months we've seen before. If we know the start |
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331 | time of the month, we can always calculate any time within the month. |
332 | The start times are calculated using a mathematical formula. Unlike |
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333 | other algorithms that do multiple calls to C<gmtime()>. |
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334 | |
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335 | The C<timelocal()> function is implemented using the same cache. We |
336 | just assume that we're translating a GMT time, and then fudge it when |
337 | we're done for the timezone and daylight savings arguments. Note that |
338 | the timezone is evaluated for each date because countries occasionally |
339 | change their official timezones. Assuming that C<localtime()> corrects |
340 | for these changes, this routine will also be correct. |
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341 | |
342 | =head1 BUGS |
343 | |
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344 | The whole scheme for interpreting two-digit years can be considered a |
345 | bug. |
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346 | |
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347 | =head1 SUPPORT |
348 | |
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349 | Support for this module is provided via the datetime@perl.org email |
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350 | list. See http://lists.perl.org/ for more details. |
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351 | |
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352 | Please submit bugs to the CPAN RT system at |
353 | http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Time-Local or via email |
354 | at bug-time-local@rt.cpan.org. |
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355 | |
356 | =head1 AUTHOR |
357 | |
358 | This module is based on a Perl 4 library, timelocal.pl, that was |
359 | included with Perl 4.036, and was most likely written by Tom |
360 | Christiansen. |
361 | |
362 | The current version was written by Graham Barr. |
363 | |
364 | It is now being maintained separately from the Perl core by Dave |
365 | Rolsky, <autarch@urth.org>. |
366 | |
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367 | =cut |