Bug or Feature?

I agree that MultiParameterAttributes handling should be refactored,
but since it probably won't be, here are a few alternatives.

You can catch the error like shown here:
http://i.nfectio.us/articles/2006/02/22/handling-invalid-dates-with-activerecord-date-helpers

Or you can just bypass Rails dates and handle freeform input using the
Chronic library like shown here:
http://i.nfectio.us/articles/2006/09/07/validate-dates-in-your-models

My suggestion is to not use the Rails Date Helpers.

Bob Silva