Thanks to Dan Wilmot for this whitepaper.
Many users need the ability to run a query against an SSAS cube that includes a date range. Typically this date range consists of a “start date” and an “end date” selection. The default behavior of dimensions in the cube makes this type of selection difficult. This paper discusses how to design your cube to include a new “Start Date” and “End Date” dimension, then how to add those dimensions to the cube, and finally how to build a named set that represents your date range. (Please note that if you do not see the link in a frame below, your network policy may be blocking it. Please check with your network admin to be sure you are able to download content from skydrive.live.com via a link in an iframe.)