Flexible date parser

I am in need of a flexible PHP date parser class that can convert written English dates (both absolute and relative) to a fixed format (e.g. YYYY-MM-DD). Importantly, the code must be CLEAN and CLEAR (with comments), in such a way that new rules/patterns can be easily added and removed, with important date manipulation functions abstracted and factored into their own methods. The class should be written as a PHP class with a public static method parse(string) and give the following results: Relative examples (assuming server has date 2009-10-08): "a day ago" => 2009-10-07 "three days ago" => 2009-10-05 "2 wks ago" => 2009-09-24 "tomorrow" => 2009-10-09 "next monday" => 2009-10-14 "next month" => 2009-11-01 "in 2 months" => 2009-12-08 "last month" => 2009-09-01 "in three days" => 2009-10-11 Absolute examples (assuming same server date as above): "November 1st" => 2009-11-01 "3 December" => 2009-12-03 "September 19 => 2010-09-19 "2010/09/10" => 2010-09-10 "2009/31/12" => 2009-12-31 (notice that yyyy/mm/dd is impossible!) "1992-10-22" => 1992-10-22 "August 23, 2010" => 2010-08-23 "31 October 1990" => 1990-11-31 ## Deliverables Must not rely on other packages, non-standard classes, etc. That is, it must be fully contained within itself and can only use what's available in the PHP5 library (no deprecated methods either).