Hi Phil

It would depend on the type of analysis you wish to perform. If you are going to be doing plenty of Date based analysis e.g. year to date , month to date and period comparrisons then I would create a specific Date table.

To take advantage of the DAX functions that operate with dates you'll need to define the table as a date table in the tabular model. This can be done from the table menu (Table/Date/ Mark as Date Table).

Cheers

-Matt