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)