Handles dates as defined by RFC 2616 section 3.3.1, and also some other non-standard, but common formats.
private const DATE_FORMATS = [ 'D, d M Y H:i:s T', 'D, d-M-y H:i:s T', 'D, d-M-Y H:i:s T', 'D, d-m-y H:i:s T', 'D, d-m-Y H:i:s T', 'D M j G:i:s Y', 'D M d H:i:s Y T', ];