unixtojd

(PHP 4, PHP 5)

unixtojd — Converteert een Unix tijd naar een Julian Day

Beschrijving

int unixtojd ([ int $timestamp ] )

Geeft een Julian Day terug voor de Unix tijd, opgegeven in de parameter timestamp (het aantal seconden vanaf 1.1.1970), of voor de huidige dag als geen parameter timestamp is opgegeven.

Zie ook jdtounix().

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Last updated: Wed, 22 Jul 2009

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unixtojd

hrabi at linuxwaves dot com
29-Mar-2007 04:02


according to http://www.decimaltime.hynes.net/dates.html#jd and reading "X. Calendar Functions" on this side, it seems that php "jd" is precisely mean as "Chronological Julian Day" (should it be named cjd, and primarily strictly mentioned - isn't it?), used for covnersion between calendar systems. Than it's ok (but Incomplete manual is strongly confusing here IMHO).

Even that, cJD is adjusted to a local time, so... I am rather babeled now, so nothing else :-).

hrabi at linuxwaves dot com
29-Mar-2007 01:33


This is unusable. Julian Day start at noon, not midnight. It's better to use Fabio solution (however there is a lurk problem with leap second).



<?php

function mmd($txt, $str_time) {

   $t = strtotime($str_time);

   $j = unixtojd($t);

   $s = gmstrftime('%D %T %Z', $t);

   $j_fabio = $t / 86400 + 2440587.5;



   printf("${txt} => (%s) %s, %s U, %s J, or %s J<br>\n", $str_time, $s, $t, $j, $j_fabio);

}



//$xt = strtotime("1.1.1970 15:00.00 GMT");

$sam = "9.10.1995 02:00.01 GMT";

$spm = "9.10.1995 22:00.01 GMT";



// unixtojd for $spm returns 2450000 (OK), but for $sam returns 2450000 too! (it is wrong).

mmd("am", $sam);  // should be 2449999 (+ 0.58334)

mmd("pm", $spm);  // should be 2450000 (+ 0.41668)

?>



reference

unix time, and UTC, TAI, ntp, ... problems: http://en.wikipedia.org/wiki/Unix_time

Julian Date Converter: http://aa.usno.navy.mil/data/docs/JulianDate.html

history overview: http://parris.josh.com.au/humour/work/17Nov1858.shtml

fabio at llgp dot org
31-Aug-2006 11:09


If you need an easy way to convert an unix timestamp to a decimal julian day you can use:



$julianDay = $unixTimeStamp / 86400 + 2440587.5;



86400 is the number of seconds in a day;

2440587.5 is the julian day at 1/1/1970 0:00 UTC.

11-Aug-2006 04:22


Its clearly stated that this function returns the Julian Day, not Julian Day + time.



If you want the time with it you will have to do something like:



$t=time();

$jd=unixtojd($t)+($t%60*60*24)/60*60*24;

johnston at capsaicin dot ca
19-Nov-2003 10:43


Also note that epoch is in UTC time (epoch is a specific point in time - epoch is not different for every time zone), so be aware of timezone complexities.

pipian at pipian dot com
12-Jun-2003 06:29


Remember that UNIX timestamps indicate a number of seconds from midnight of January 1, 1970 on the Gregorian calendar, not the Julian Calendar.

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Last updated: Wed, 22 Jul 2009