Multiple Dates in one Model - Yikes! An Error!

Hello Everyone, I encountered this issue recently. I was importing data that had multiple date columns: Start Date, End Date, & Another Date field. I couldn't get past the modelling stage because BOC wouldn't let me set "date" as a dimension for more than one column. Another question is, if have separate columns that says the day of the month, the month, and the year, how would I treat them? Dates? Generic Dimensions? I would appreciate your advice on this topic!