How do I convert the date format  from 2012-03-19T22:10:56.000Z to Wed Nov 13 18:06:37 +0000 2013 without using string functions like substr. This date format is being used by Gnip. Not sure what format it is. 
I tried using the date function
$postedTime = "2012-03-19T22:10:56.000Z";
date($postedTime,"D M d H:i:s O Y"); 
But I get an error since $postedTime is a string and not long variable.