unixtojd

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fabio at llgp dot org
31-Aug-2006 05:09


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 10:22


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;

warhog at warhog d0t net
13-Jul-2005 05:11


Well, that's neither a bug, nor an interesting quirk.. The explanation is quite simple:



The Integer containing a julian date (jd) only stores the date, not the time. When you convert a unix-timestamp, which stores also the time, into a jd, the time-information won't be transferred into the jd. When converting back the jd into a unix-timestamp, you'll get a timestamp for the specific day at 2 o'clock am. ( 02:00:00 )



Sample:

    Timestamp: 1121206013

    JD: 2453565



    Timestamp from JD: 1121212800



    Original Timestamp "d.m.y H:i:s": 13.07.2005 00:06:53

    Timstamp from JD "d.m.y H:i:s": 13.07.2005 02:00:00



greetz

Mike
22-Dec-2004 12:57


Interesting quirk ... maybe bug.

If you use today = unixtojd(time())

then use jdtounix(today) the result is one day short of today.

johnston at capsaicin dot ca
20-Nov-2003 05:43


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
13-Jun-2003 12:29


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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unixtojd

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