is_datestamp('Thu, 14 Dec 2006 00:20:24 -0480', [1166074824, '-0520']);
is_datestamp('Mon, 14 Apr 2014 07:59:01 -0007', [1397462761, '-0007']);
is_datestamp('Thu, 14 Dec 2006 00:20:24 -0480', [1166074824, '-0520']);
is_datestamp('Mon, 14 Apr 2014 07:59:01 -0007', [1397462761, '-0007']);