NAME

Time::Local::TZ - time converter functions with localtime-based interface

SYNOPSIS

  use Time::Local::TZ qw/:const :func/;

  # get localtime-like result for given timezone and unixtime
  ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = tz_localtime("Europe/Moscow" => $epoch);
  ($asctime) = tz_localtime("Europe/Moscow" => 0);      # Thu Jan  1 03:00:00 1970

  # get unixtime for given timezone and localtime data
  $epoch = tz_timelocal("Europe/Moscow" => $sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst);
  $epoch = tz_timelocal("Europe/Moscow" => $sec,$min,$hour,$mday,$mon,$year);    # the same

  # truncate unixtime to the beginning of minute/hour/day/month/year (of course, in given timezone)
  $epoch2 = tz_truncate("Europe/Moscow", $epoch, TM_HOUR());

  # get offset (in seconds) between given timezone and UTC (for the given moment)
  $tz_offset_seconds = tz_offset("Europe/Moscow" => $epoch);
  $tz_offset_seconds = tz_offset("Europe/Moscow");   

  # convert localtime data from one timezone to another
  @localtime_berlin = tz_localtime("Europe/Berlin", tz_timelocal("Europe/Moscow", @localtime_moscow));

  # constants to navigate @localtime (and to use with tz_offset function)
  @localtime = tz_localtime("UTC", $epoch);
  $date_str = sprintf "%04d-%02d-%02d", @localtime[TM_YEAR()+1900, TM_MON()+1, TM_MDAY()];   # 1970-01-01
  $time_str = sprintf "%02d:%02d:%02d", @localtime[TM_HOUR(),      TM_MIN(),   TM_SEC() ];   # 13:25:59
  $weekday = $localtime[ TM_WDAY() ];
  $yearday = $localtime[ TM_YDAY() ];
  $isdst   = $localtime[ TM_ISDST() ];

DESCRIPTION

This module provides a set of functions to convert time between timezones and do some other timezone-dependant operations. Most functions work with localtime-like arrays, so they can be easily integrated with other modules supporting this format. Module is written in XS, so it is fast enough.

FUNCTIONS

@localtime = tz_localtime($timezone_name, $epoch)

Works similar to build-in localtime function, but works with timezone you provide, instead of system timezone. Both arguments are mandatory.

In scalar context, tz_localtime returns the asctime(3) value (without trailing \n, like localtime):

  $date_string = tz_localtime("Europe/Moscow" => time());  # e.g., "Thu Apr 27 15:35:34 2017"

In list context, converts time provided to a 9-element list with the time analyzed for the given timezone:

  #  0    1    2     3     4    5     6     7     8
  ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = tz_localtime("Europe/Moscow" => time);

  @localtime = tz_localtime("Europe/Moscow" => time);
  $date_string = POSIX::strftime("%d %B %Y, %H:%M", @localtime);

Values $mday, $year, $wday, $yday have special format, which can confuse beginners. See localtime function for details.

$epoch = tz_timelocal($timezone_name, @localtime)

Works similar to timelocal function from Time::Local module, but works with timezone you provide, instead of system timezone. Returns unixtime value for the localtime data and timezone provided. All arguments are mandatory, except $wday, $yday, $isdst.

  $epoch = tz_timelocal("Europe/Moscow" => $sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst);
  $epoch = tz_timelocal("Europe/Moscow" => $sec,$min,$hour,$mday,$mon,$year);

  $data_string = "2017-04-27 15:35:34";
  @localtime = POSIX::strptime($data_string, "%Y-%m-%d %H:%M:%S");
  $epoch = tz_timelocal("Europe/Moscow" => @localtime);
$epoch = tz_truncate($timezone, $epoch, $unit)

This function calculates tz_localtime for the timezone and unixtime provided, resets fields with index smaller than $unit and calculates unixtime back. This can be useful to get unixtime for first second of the interval unit (year/month/day/hour/minute) which $epoch belongs to. All arguments are mandatory. It is recommended to use TM_* constants from this module to specify $unit.

  $data_string = "1970-03-08 05:25:45";
  @localtime = POSIX::strptime($data_string, "%Y-%m-%d %H:%M:%S");
  $epoch = tz_timelocal("Europe/Moscow" => @localtime);              # 5711145
  
  $epoch2 = tz_truncate("Europe/Moscow" => $epoch, TM_HOUR());       # 5709600
  print tz_localtime("Europe/Moscow" => $epoch2);                    # Sun Mar  8 05:00:00 1970
  
  $epoch2 = tz_truncate("Europe/Moscow" => $epoch, TM_YEAR());       # -10800
  print tz_localtime("Europe/Moscow" => $epoch2);                    # Thu Jan  1 00:00:00 1970
  
  # of course, in other timezones this alignment is wrong:
  print tz_localtime("Europe/Berlin" => $epoch2);                    # Wed Dec 31 22:00:00 1969
$offset_seconds = tz_offset($timezone, $epoch)

Calculates offset (in seconds) from UTC to provided timezone, actual for the given unixtime. Both arguments are mandatory.

  print tz_offset("Europe/Moscow", 1293829200); # 10800 (+3 hours for the date 2011-01-01)
  print tz_offset("Europe/Moscow", 1309464000); # 14400 (+4 hours for the date 2011-07-01)

CONSTANTS

TM_SEC, TM_MIN, TM_HOUR, TM_MDAY, TM_MON, TM_YEAR, TM_WDAY, TM_YDAY, TM_ISDST

These constants can be useful to navigate on localtime and tz_localtime arrays:

    @localtime = tz_localtime("Europe/Moscow" => time);
    printf "Time is is %02d:%02d:%02d", @localtime[ TM_HOUR(), TM_MIN(), TM_SEC() ];

It is recommended to use them with tz_truncate function:

  $epoch2 = tz_truncate("Europe/Moscow" => $epoch, TM_HOUR());       # 5709600

NOTES AND CAVEATS

This module uses your operating system rules to convert time. They are based on environment variable TZ and can differ from OS to OS. Many modern OSes (including Linux and FreeBSD) support Olson timezone names (like Europe/Berlin, America/New_York etc.), which is the only recommended way to use with this module. Other OSes usually know only POSIX timezone names. You can deal with them too, but the result can be inconsistent. There is no native Olson db support in Windows, but CYGWIN solves this.

Please note that set of timezone rules is not something permanent, they are refreshed up to several times per month. So, to get correct results from this module you should always have fresh timezone information in your OS. If you don't want to do this, take a look on "DateTime::TimeZone", which have its own timezones database inside. Anyway, you should update it on a regular basis too.

This module works with process environment, so it is not thread-safe.

This module works with mod_perl2 (at least in non-threaded mode). mod_perl2 has problem with %ENV. Unlike mod_perl1 and usual perl programs %ENV under mod_perl2 is untied from process environment. So, even if you change $ENV{TZ}, built-in functions (like localtime) will know nothing about it, because real process environment is untouched. This module works with environment bypassing perl %ENV, so in mod_perl2 prefork mode it works fine.

SEE ALSO

To get more information about "localtime" format, see "localtime" in perlfunc and "timelocal" in Time::Local.

If you are interested in useful functions to work with "localtime" data, see "strftime" in POSIX and POSIX::strptime.

If you want to know more on alternative modules to convert time between timezones, see DateTime and DateTime::TimeZone.

If you want to know more about environment variable TZ and it's formats, you can look at the articles below: http://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html https://www.ibm.com/developerworks/aix/library/au-aix-posix/

SOURCE

The development version is on github at https://github.com/bambr/Time-Local-TZ

AUTHOR

Sergey Panteleev, <bambr@cpan.org>

COPYRIGHT AND LICENSE

Copyright (C) 2017 by Sergey Panteleev

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.8 or, at your option, any later version of Perl 5 you may have available.