{ "mode": "perldoc", "parameter": "Time::Local", "section": "", "url": "https://www.chedong.com/phpMan.php/perldoc/Time%3A%3ALocal/json", "generated": "2026-06-03T03:35:19Z", "synopsis": "use Time::Local qw( timelocalposix timegmposix );\nmy $time = timelocalposix( $sec, $min, $hour, $mday, $mon, $year );\nmy $time = timegmposix( $sec, $min, $hour, $mday, $mon, $year );", "sections": { "NAME": { "content": "Time::Local - Efficiently compute time from local and GMT time\n", "subsections": [] }, "VERSION": { "content": "version 1.30\n", "subsections": [] }, "SYNOPSIS": { "content": "use Time::Local qw( timelocalposix timegmposix );\n\nmy $time = timelocalposix( $sec, $min, $hour, $mday, $mon, $year );\nmy $time = timegmposix( $sec, $min, $hour, $mday, $mon, $year );\n", "subsections": [] }, "DESCRIPTION": { "content": "This module provides functions that are the inverse of built-in perl functions \"localtime()\" and\n\"gmtime()\". They accept a date as a six-element array, and return the corresponding time(2)\nvalue in seconds since the system epoch (Midnight, January 1, 1970 GMT on Unix, for example).\nThis value can be positive or negative, though POSIX only requires support for positive values,\nso dates before the system's epoch may not work on all operating systems.\n\nIt is worth drawing particular attention to the expected ranges for the values provided. The\nvalue for the day of the month is the actual day (i.e. 1..31), while the month is the number of\nmonths since January (0..11). This is consistent with the values returned from \"localtime()\" and\n\"gmtime()\".\n", "subsections": [] }, "FUNCTIONS": { "content": "\"timelocalposix()\" and \"timegmposix()\"\nThese functions are the exact inverse of Perl's built-in \"localtime\" and \"gmtime\" functions.\nThat means that calling \"timelocalposix( localtime($value) )\" will always give you the same\n$value you started with. The same applies to \"timegmposix( gmtime($value) )\".\n\nThe one exception is when the value returned from \"localtime()\" represents an ambiguous local\ntime because of a DST change. See the documentation below for more details.\n\nThese functions expect the year value to be the number of years since 1900, which is what the\n\"localtime()\" and \"gmtime()\" built-ins returns.\n\nThey perform range checking by default on the input $sec, $min, $hour, $mday, and $mon values\nand will croak (using \"Carp::croak()\") if given a value outside the allowed ranges.\n\nWhile it would be nice to make this the default behavior, that would almost certainly break a\nlot of code, so you must explicitly import these functions and use them instead of the default\n\"timelocal()\" and \"timegm()\".\n\nYou are strongly encouraged to use these functions in any new code which uses this module. It\nwill almost certainly make your code's behavior less surprising.\n\n\"timelocalmodern()\" and \"timegmmodern()\"\nWhen \"Time::Local\" was first written, it was a common practice to represent years as a two-digit\nvalue like 99 for 1999 or 1 for 2001. This caused all sorts of problems (google \"Y2K problem\" if\nyou're very young) and developers eventually realized that this was a terrible idea.\n\nThe default exports of \"timelocal()\" and \"timegm()\" do a complicated calculation when given a\nyear value less than 1000. This leads to surprising results in many cases. See \"Year Value\nInterpretation\" for details.\n\nThe \"time*modern()\" functions do not do this year munging and simply take the year value as\nprovided.\n\nThey perform range checking by default on the input $sec, $min, $hour, $mday, and $mon values\nand will croak (using \"Carp::croak()\") if given a value outside the allowed ranges.\n\n\"timelocal()\" and \"timegm()\"\nThis module exports two functions by default, \"timelocal()\" and \"timegm()\".\n\nThey perform range checking by default on the input $sec, $min, $hour, $mday, and $mon values\nand will croak (using \"Carp::croak()\") if given a value outside the allowed ranges.\n\nWarning: The year value interpretation that these functions and their nocheck variants use will\nalmost certainly lead to bugs in your code, if not now, then in the future. You are strongly\ndiscouraged from using these in new code, and you should convert old code to using either the\n*posix or *modern functions if possible.\n\n\"timelocalnocheck()\" and \"timegmnocheck()\"\nIf you are working with data you know to be valid, you can use the \"nocheck\" variants,\n\"timelocalnocheck()\" and \"timegmnocheck()\". These variants must be explicitly imported.\n\nIf you supply data which is not valid (month 27, second 1,000) the results will be unpredictable\n(so don't do that).\n\nNote that my benchmarks show that this is just a 3% speed increase over the checked versions, so\nunless calling \"Time::Local\" is the hottest spot in your application, using these nocheck\nvariants is unlikely to have much impact on your application.\n", "subsections": [ { "name": "Year Value Interpretation", "content": "This does not apply to the *posix or *modern functions. Use those exports if you want to\nensure consistent behavior as your code ages.\n\nStrictly speaking, the year should be specified in a form consistent with \"localtime()\", i.e.\nthe offset from 1900. In order to make the interpretation of the year easier for humans,\nhowever, who are more accustomed to seeing years as two-digit or four-digit values, the\nfollowing conventions are followed:\n\n* Years greater than 999 are interpreted as being the actual year, rather than the offset from\n1900. Thus, 1964 would indicate the year Martin Luther King won the Nobel prize, not the\nyear 3864.\n\n* Years in the range 100..999 are interpreted as offset from 1900, so that 112 indicates 2012.\nThis rule also applies to years less than zero (but see note below regarding date range).\n\n* Years in the range 0..99 are interpreted as shorthand for years in the rolling \"current\ncentury,\" defined as 50 years on either side of the current year. Thus, today, in 1999, 0\nwould refer to 2000, and 45 to 2045, but 55 would refer to 1955. Twenty years from now, 55\nwould instead refer to 2055. This is messy, but matches the way people currently think about\ntwo digit dates. Whenever possible, use an absolute four digit year instead.\n\nThe scheme above allows interpretation of a wide range of dates, particularly if 4-digit years\nare used. But it also means that the behavior of your code changes as time passes, because the\nrolling \"current century\" changes each year.\n" }, { "name": "Limits of timet", "content": "On perl versions older than 5.12.0, the range of dates that can be actually be handled depends\non the size of \"timet\" (usually a signed integer) on the given platform. Currently, this is 32\nbits for most systems, yielding an approximate range from Dec 1901 to Jan 2038.\n\nBoth \"timelocal()\" and \"timegm()\" croak if given dates outside the supported range.\n\nAs of version 5.12.0, perl has stopped using the time implementation of the operating system\nit's running on. Instead, it has its own implementation of those routines with a safe range of\nat least +/- 252 (about 142 million years)\n\nAmbiguous Local Times (DST)\nBecause of DST changes, there are many time zones where the same local time occurs for two\ndifferent GMT times on the same day. For example, in the \"Europe/Paris\" time zone, the local\ntime of 2001-10-28 02:30:00 can represent either 2001-10-28 00:30:00 GMT, or 2001-10-28 01:30:00\nGMT.\n\nWhen given an ambiguous local time, the timelocal() function will always return the epoch for\nthe *earlier* of the two possible GMT times.\n\nNon-Existent Local Times (DST)\nWhen a DST change causes a locale clock to skip one hour forward, there will be an hour's worth\nof local times that don't exist. Again, for the \"Europe/Paris\" time zone, the local clock jumped\nfrom 2001-03-25 01:59:59 to 2001-03-25 03:00:00.\n\nIf the \"timelocal()\" function is given a non-existent local time, it will simply return an epoch\nvalue for the time one hour later.\n" }, { "name": "Negative Epoch Values", "content": "On perl version 5.12.0 and newer, negative epoch values are fully supported.\n\nOn older versions of perl, negative epoch (\"timet\") values, which are not officially supported\nby the POSIX standards, are known not to work on some systems. These include MacOS (pre-OSX) and\nWin32.\n\nOn systems which do support negative epoch values, this module should be able to cope with dates\nbefore the start of the epoch, down the minimum value of timet for the system.\n" } ] }, "IMPLEMENTATION": { "content": "These routines are quite efficient and yet are always guaranteed to agree with \"localtime()\" and\n\"gmtime()\". We manage this by caching the start times of any months we've seen before. If we\nknow the start time of the month, we can always calculate any time within the month. The start\ntimes are calculated using a mathematical formula. Unlike other algorithms that do multiple\ncalls to \"gmtime()\".\n\nThe \"timelocal()\" function is implemented using the same cache. We just assume that we're\ntranslating a GMT time, and then fudge it when we're done for the timezone and daylight savings\narguments. Note that the timezone is evaluated for each date because countries occasionally\nchange their official timezones. Assuming that \"localtime()\" corrects for these changes, this\nroutine will also be correct.\n", "subsections": [] }, "AUTHORS EMERITUS": { "content": "This module is based on a Perl 4 library, timelocal.pl, that was included with Perl 4.036, and\nwas most likely written by Tom Christiansen.\n\nThe current version was written by Graham Barr.\n", "subsections": [] }, "BUGS": { "content": "The whole scheme for interpreting two-digit years can be considered a bug.\n\nBugs may be submitted at .\n\nThere is a mailing list available for users of this distribution, .\n\nI am also usually active on IRC as 'autarch' on \"irc://irc.perl.org\".\n", "subsections": [] }, "SOURCE": { "content": "The source code repository for Time-Local can be found at\n.\n", "subsections": [] }, "AUTHOR": { "content": "Dave Rolsky \n", "subsections": [] }, "CONTRIBUTORS": { "content": "* Florian Ragwitz \n\n* J. Nick Koston \n\n* Unknown \n", "subsections": [] }, "COPYRIGHT AND LICENSE": { "content": "This software is copyright (c) 1997 - 2020 by Graham Barr & Dave Rolsky.\n\nThis is free software; you can redistribute it and/or modify it under the same terms as the Perl\n5 programming language system itself.\n\nThe full text of the license can be found in the LICENSE file included with this distribution.\n", "subsections": [] } }, "summary": "Time::Local - Efficiently compute time from local and GMT time", "flags": [], "examples": [], "see_also": [] }