We will try to be as tolerant as possible of different representations, since
RSS Is A Fucking Mess, broken dates seem to be especially pervasive, etc.
Supports anything that your version of PHP's strtotime() can handle; also has
a built-in parser for W3C DTF, in case your PHP doesn't have that.
Tries to parse a W3C DTF first; then falls back to strtotime(). If strtotime
fails due to a mystery timezone, then we will try again on local time, with
the timezone stripped out.
To parse a string representation of a date-time from a feed, instantiate and
then pull the timestamp:
$time = new FeedTime($s);
if (!$time->failed()) :
$ts = $time->timestamp();
else :
...
endif;