GeoFlow Time Line vs. Date Dimension data type

Hi all,

I've got a PowerPivot query in from my data warehouse and flattened all dimension attributes and measures that I want for the GeoFlow visualization.  As you all know, the date dimension stores dates in integer types, like 20051018 is 10/18/2005.  After looking at some YouTube videos, I noticed that GeoFlow might be expecting an actual date format (and/or a datetime format).  I've CAST real dates from the integers and brought them back into PowerPivot.  Everything refreshed okay, so I know the data is good. 

Yet when I try to drag the date field, or the datetime version of the field (as in 10/18/2005 12:00:00.000), GeoFlow won't let me drop it into the TIME bucket.  Nor will it let me select it (box) in the field list.  I have also just tried to use the Year integer from dimDate and that didn't work either. 

Question: what is the proper data type for date visualizations using the time slicer for time-based animations (by year)?

I notice that the TimeLine and Time Decorator buttons in the ribbon are greyed out??  This suggests to me that it's not getting the date and/or datetime data types in the query??

At this point I'm confused and exhausted bing searches.

Thanks in advance,
Scott