I have a customer who has a fiscal year that starts in October. I noted that when loading the time dimension. Now I am going to load the measure with fiscal year and period (month). So for example, October 2007 is year 2008 period 1. My question is which of the "date mapping" options should I select? I know it's not measure dt determines time, but I can't find any documentation on the differences for Time Dim determines ...

Can you please make a recommendation.

Thanks.

You'd select most probably time dimension determines measure date. Your source data would specify the time dimension linkage directly. You could select (first) or (last) safely; either will work.