as i understand it, match will not work with dropdown lists or radio button entries,

match will not work with dropdown lists or radio button entries

Correct. Sorry, I was thinking of text boxes and not other selection lists. I don't think there's a workaround for that problem.

this seems to work, the date field can not be empty in this way.

[[form]]
fields: 
 date:
  type: text
  hint: jj-mm-aa
  label: Date
  match: "/^\s*\S.*$/"
[[/form]]

My snippet would work best for date fields:

http://snippets.wikidot.com/code:regexp-date-wizard