Perhaps rather than expand the reverse parser, it would be more effective to build (or obtain) a UI for entering dates. I'm thinking of the ubiquitous clickable calendars used for entering dates on the web.
Danny
I consider the reverse parsing less of a priority since it is on the professor side. I've never seen problems with that since in all our use cases (and I think almost all instances in WeBWorK), when a professor is entering a date, they are only editing data in a pre-filled form field, so they never have to try to type it from scratch.