Date column for External Rollup Measure

[jage]

Hi,

Having problems with associating a date for an External Rollup measure.

My date dimension is the standard Year, Quarter, Month. It is generated from a query that has date in the standard format and builds a regular rollup measure.

My query for the external rollup measure has month, product group, store number and number of transactions.

What format does the month need to be in the query and how do I associate it to my date dimension?

Thanks