DateTime::Calendar::Julian

Section: User Contributed Perl Documentation (3)
Updated: 2021-01-27
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NAME

DateTime::Calendar::Julian - Dates in the Julian calendar

SYNOPSIS

  use DateTime::Calendar::Julian;

  $dt = DateTime::Calendar::Julian->new( year  => 964,
                                         month => 10,
                                         day   => 16,
                                       );

  # convert Julian->Gregorian...

  $dtgreg = DateTime->from_object( object => $dt );
  print $dtgreg->datetime;  # prints '0964-10-21T00:00:00'

  # ... and back again

  $dtjul = DateTime::Calendar::Julian->from_object( object => $dtgreg );
  print $dtjul->datetime;  # prints '0964-10-16J00:00:00'

DESCRIPTION

DateTime::Calendar::Julian implements the Julian Calendar. This module implements all methods of DateTime; see the DateTime(3) manpage for all methods.

METHODS

This module implements one additional method besides the ones from DateTime, and changes the output of one other method.

•

gregorian_deviation

Returns the difference in days between the Gregorian and the Julian calendar.

•

datetime

  print $dt->datetime( $sep ), "\n";

This method is equivalent to

  join $sep, $dt->ymd( '-' ), $dt->hms( ':' );

The $sep argument defaults to 'J'.

Caveat: the optional argument was added to this method in version 1.02, to belatedly track a change made in DateTime version 1.43 released 2017-05-29. Fixing this restores the original stringification behavior of this class, which was to return an ISO-8601 string unless a formatter was set. Before this change, the stringification separated date and time with either a 'T' or a 'J', depending on which version of DateTime was installed.

BACKGROUND

The Julian calendar was introduced by Julius Caesar in 46BC. It featured a twelve-month year of 365 days, with a leap year in February every fourth year. This calendar was adopted by the Christian church in 325AD. Around 532AD, Dionysius Exiguus moved the starting point of the Julian calendar to the calculated moment of birth of Jesus Christ. Apart from differing opinions about the start of the year (often January 1st, but also Christmas, Easter, March 25th and other dates), this calendar remained unchanged until the calendar reform of pope Gregory XIII in 1582. Some backward countries, however, used the Julian calendar until the 18th century or later.

This module uses the proleptic Julian calendar for years before 532AD, or even 46BC. This means that dates are calculated as if this calendar had existed unchanged from the beginning of time. The assumption is made that January 1st is the first day of the year.

Note that BC years are given as negative numbers, with 0 denoting the year 1BC (there was no year 0AD!), -1 the year 2BC, etc.

SUPPORT

Support for this module is provided via the datetime@perl.org email list. See <https://lists.perl.org/> for more details.

Please report bugs to <https://github.com/trwyant/perl-DateTime-Calendar-Julian/issues>, or in electronic mail to wyant@cpan.org.

AUTHOR

Eugene van der Pijll <pijll@gmx.net>

Thomas R. Wyant, III wyant at cpan dot org

COPYRIGHT AND LICENSE

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

This program is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose.