Michael G Schwern > Time-y2038 > Time::y2038

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NAME ^

Time::y2038 - Versions of Perl's time functions which work beyond 2038

SYNOPSIS ^

    use Time::y2038;

    print scalar gmtime 2**52;  # Sat Dec  6 03:48:16 142715360

DESCRIPTION ^

On many computers, Perl's time functions will not work past the year 2038. This is a design fault in the underlying C libraries Perl uses. Time::y2038 provides replacements for those functions which will work accurately +/1 142 million years.

This only imports the functions into your namespace. To replace it everywhere, see Time::y2038::Everywhere.

Replaces the following functions:

gmtime()

See "gmtime" in perlfunc for details.

localtime()

See "localtime" in perlfunc for details.

timegm()

    my $time = timegm($sec, $min, $hour, $month_day, $month, $year);

The inverse of gmtime(), takes a date and returns the coorsponding $time (number of seconds since Midnight, January 1st, 1970 GMT). All values are the same as gmtime() so $month is 0..11 (January is 0) and the $year is years since 1900 (2008 is 108).

    # June 4, 1906 03:02:01 GMT
    my $time = timegm(1, 2, 3, 4, 5, 6);

timegm() can take two additional arguments which are always ignored. This lets you feed the results from gmtime() back into timegm() without having to strip the arguments off.

The following is always true:

    timegm(gmtime($time)) == $time;

timelocal()

    my $time = timelocal($sec, $min, $hour, $mday, $month, $year);
    my $time = timelocal($sec, $min, $hour, $mday, $month, $year, $wday, $yday, $isdst);

Like timegm(), but interprets the date in the current time zone.

timelocal() will normally figure out if daylight savings time is in effect, but if $isdst is given this will override that check. This is mostly useful to resolve ambiguous times around "fall back" when the hour between 1am and 2am occurs twice.

    # Sun Nov  4 00:59:59 2007
    print timelocal(59, 59, 0, 4, 10, 107);  # 1194163199

    # Sun Nov  4 01:00:00 2007 DST, one second later
    print timelocal(0, 0, 1, 4, 10, 107, undef, undef, 1);  # 1194163200

    # Sun Nov  4 01:00:00 2007 no DST, one hour later
    print timelocal(0, 0, 1, 4, 10, 107, undef, undef, 0);  # 1194166800

$wday and $yday are ignored. They are only there for compatibility with the return value of localtime().

LIMITATIONS ^

The safe range of times is +/ 2**52 (about 142 million years).

Although the underlying time library can handle times from -2**63 to 2**63-1 (about +/- 292 billion years) Perl uses floating point numbers internally and so accuracy degrates after 2**52.

BUGS & FEEDBACK ^

See http://rt.cpan.org/Dist/Display.html?Queue=Time-y2038 to report and view bugs.

If you like the module, please drop the author an email.

The latest version of this module can be found at http://y2038.googlecode.com/ and the repository is at http://y2038.googlecode.com/svn/trunk/ in perl/Time-y2038. You have to check out the whole repository because there are symlinks.

AUTHOR ^

Michael G Schwern <schwern@pobox.com>

LICENSE & COPYRIGHT ^

Copyright 2008-2010 Michael G Schwern

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

See http://www.perl.com/perl/misc/Artistic.html

SEE ALSO ^

Time::y2038::Everywhere overrides localtime() and gmtime() across the whole program.

The y2038 project at http://y2038.googlecode.com/

http://xkcd.com/376/

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