DateTime::Format::Epoch::JD(3pm)			User Contributed Perl Documentation			  DateTime::Format::Epoch::JD(3pm)

NAME

       DateTime::Format::Epoch::JD - Convert DateTimes to/from Julian Days

SYNOPSIS

	 use DateTime::Format::Epoch::JD;

	 my $dt = DateTime::Format::Epoch::JD->parse_datetime( 2453244.5 );
	  # 2004-08-27T00:00:00
	 DateTime::Format::Epoch::JD->format_datetime($dt);
	  # 2453244.5

	 my $formatter = DateTime::Format::Epoch::JD->new();
	 my $dt2 = $formatter->parse_datetime( 2453244.5 );
	  # 2004-08-27T00:00:00
	 $formatter->format_datetime($dt2);
	  # 2453244.5

DESCRIPTION

       This module can convert a DateTime object (or any object that can be converted to a DateTime object) to the Julian Day number. This is the
       number of days since noon U.T.C. on January 1, 4713 B.C. (Julian calendar).

       This time scale was originally proposed by John Herschel, and is often used in astronomical calculations.

       Similar modules are:

       o   DateTime::Format::Epoch::MJD

	   Implements the "modified Julian Day", starting at midnight U.T.C., November 17, 1858.  This number is always 2,400,000.5 lower than the
	   JD, and this count only uses five digits to specify a date between 1859 and about 2130.

       o   DateTime::Format::Epoch::RJD

	   Implements the "reduced Julian Day", starting at noon U.T.C., November 16, 1858.  This number is always 2,400,000 lower than the JD.

       o   DateTime::Format::Epoch::TJD

	   Implements the "truncated Julian Day", starting at midnight U.T.C., May 24, 1968.  This number is always 2,440,000,5 lower than the JD.
	   Actually, there is another version of the TJD, defined as JD modulo 10,000.	But that one is a bit harder to implement, so you'll have
	   to do with this version of TJD.  Or don't use TJD's at all.

       o   DateTime::Format::Epoch::RataDie

	   Implements the Rata Die count, starting at January 1, 1 (Gregorian).  This count is used by DateTime::Calendar programmers.

       o   DateTime::Format::Epoch::Lilian

	   Implements the Lilian count, named after Aloysius Lilian (a 16th century physician) and first used by IBM (a 19th century punched card
	   machine manufacturer).  This counts the number of days since the adoption of the Gregorian calendar.  Only days are counted, and
	   October 15, 1584 is day 1.

METHODS

       Most of the methods are the same as those in DateTime::Format::Epoch.  The only difference is the constructor.

       o   new()

	   Constructor of the formatter/parser object. It has no parameters.

SUPPORT

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

AUTHOR

       Eugene van der Pijll <pijll@gmx.net>

COPYRIGHT

       Copyright (c) 2004 Eugene van der Pijll.  All rights reserved.  This program is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.

SEE ALSO

       DateTime

       datetime@perl.org mailing list

perl v5.10.1							    2007-12-03					  DateTime::Format::Epoch::JD(3pm)