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(PHP 4, PHP 5, PHP 7)

unixtojdConvert Unix timestamp to Julian Day


int unixtojd ([ int $timestamp = time() ] )

Return the Julian Day for a Unix timestamp (seconds since 1.1.1970), or for the current day if no timestamp is given.



A unix timestamp to convert.

Valorile întoarse

A julian day number as integer.

A se vedea și

  • jdtounix() - Convert Julian Day to Unix timestamp

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User Contributed Notes 6 notes

hrabi at linuxwaves dot com
10 years ago
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).

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)

unix time, and UTC, TAI, ntp, ... problems:
Julian Date Converter:
history overview:
fabio at llgp dot org
10 years ago
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.
10 years ago
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:

hrabi at linuxwaves dot com
10 years ago
according to 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 :-).
johnston at capsaicin dot ca
13 years ago
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
14 years ago
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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