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.IX Title "Time::JulianDay 3"
.TH Time::JulianDay 3 2025-07-14 "perl v5.42.0" "User Contributed Perl Documentation"
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.SH NAME
Time::JulianDay \-\- Julian calendar manipulations
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\&        use Time::JulianDay
\&
\&        $jd = julian_day($year, $month_1_to_12, $day)
\&        $jd = local_julian_day($seconds_since_1970);
\&        $jd = gm_julian_day($seconds_since_1970);
\&        ($year, $month_1_to_12, $day) = inverse_julian_day($jd)
\&        $dow = day_of_week($jd) 
\&
\&        print (Sun,Mon,Tue,Wed,Thu,Fri,Sat)[$dow];
\&
\&        $seconds_since_jan_1_1970 = jd_secondslocal($jd, $hour, $min, $sec)
\&        $seconds_since_jan_1_1970 = jd_secondsgm($jd, $hour, $min, $sec)
\&        $seconds_since_jan_1_1970 = jd_timelocal($sec,$min,$hours,$mday,$month_0_to_11,$year)
\&        $seconds_since_jan_1_1970 = jd_timegm($sec,$min,$hours,$mday,$month_0_to_11,$year)
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
JulianDay is a package that manipulates dates as number of days since 
some time a long time ago.  It\*(Aqs easy to add and subtract time
using julian days...
.PP
The day_of_week returned by \fBday_of_week()\fR is 0 for Sunday, and 6 for
Saturday and everything else is in between.
.SH ERRATA
.IX Header "ERRATA"
Time::JulianDay is not a correct implementation.  There are two
problems.  The first problem is that Time::JulianDay only works
with integers.  Julian Day can be fractional to represent time
within a day.  If you call \fBinverse_julian_day()\fR with a non\-integer
time, it will often give you an incorrect result.
.PP
The second problem is that Julian Days start at noon rather than
midnight.  The \fBjulian_day()\fR function returns results that are too
large by 0.5.
.PP
What to do about these problems is currently open for debate.  I\*(Aqm
tempted to leave the current functions alone and add a second set
with more accurate behavior.
.PP
There is another implementation in Astro::Time that may be more accurate.
.SH GENESIS
.IX Header "GENESIS"
Written by David Muir Sharnoff <cpan@dave.sharnoff.org> with help from
previous work by 
Kurt Jaeger aka PI <zrzr0111@helpdesk.rus.uni\-stuttgart.de>
 	based on postings from: Ian Miller <ian_m@cix.compulink.co.uk>;
Gary Puckering <garyp%cognos.uucp@uunet.uu.net>
	based on Collected Algorithms of the ACM ?;
and the unknown\-to\-me author of Time::Local.
.SH LICENSE
.IX Header "LICENSE"
Copyright (C) 1996\-1999 David Muir Sharnoff.  License hereby
granted for anyone to use, modify or redistribute this module at
their own risk.  Please feed useful changes back to cpan@dave.sharnoff.org.