If you need an easy way to convert a decimal julian day to an unix timestamp you can use:
$unixTimeStamp = ($julianDay - 2440587.5) * 86400;
2440587.5 is the julian day at 1/1/1970 0:00 UTC
86400 is the number of seconds in a day
jdtounix
(PHP 4, PHP 5, PHP 7, PHP 8)
jdtounix — Convert Julian Day to Unix timestamp
Description
This function will return a Unix timestamp corresponding to the
Julian Day given in julian_day. The time returned is
UTC.
Parameters
-
julian_day -
A julian day number between
2440588and106751993607888on 64bit systems, or between2440588and2465443on 32bit systems.
Return Values
The unix timestamp for the start (midnight, not noon) of the given Julian day
Errors/Exceptions
If julian_day is outside of the allowed range,
a ValueError is thrown.
Changelog
| Version | Description |
|---|---|
| 8.0.0 |
This function no longer returns false on failure, but raises a
ValueError instead.
|
| 7.3.24, 7.4.12 |
The upper limit of julian_day has been extended. Previously,
it was 2465342 regardless of the architecture.
|
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User Contributed Notes 5 notes
fabio at llgp dot org ¶
18 years ago
Anonymous ¶
19 years ago
Warning: the calender functions involving julian day operations seem to ignore the decimal part of the julian day count.
This means that the returned date is wrong 50% of the time, since a julian day starts at decimal .5 . Take care!!
seb at carbonauts dot com ¶
21 years ago
Remember that unixtojd() assumes your timestamp is in GMT, but jdtounix() returns a timestamp in localtime.
This fooled me a few times.
So if you have:
$timestamp1 = time();
$timestamp2 = jdtounix(unixtojd($timestamp1));
Unless your localtime is the same as GMT, $timestamp1 will not equal $timestamp2.
pipian at pipian dot com ¶
21 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.
Saeed Hubaishan ¶
10 years ago
unixtojd() assumes that your timestamp is in GMT, but jdtounix() returns a timestamp in localtime.
so
<?php
$d1=jdtogregorian(unixtojd(time()));
$d2= gmdate("m/d/Y");
$d3=date("m/d/Y");
?>
$d1 always equals $d2 but $d1 may differ from $d3
