KPI Visual (Blank) on date span using .[Date]

I was trying to use the KPI visual of a moving average measure, over a series of dates ( non-unique, so there are many duplicate dates).  I was having a bizarre problem with the dates that came from Salesforce Objects as they are date/time/timezone format, however, their type could not be changed simply to date.  I would get an error mentioning that I cannot aggregate data using a limit funtion.  So I just duplicated the column in the query with a custom column and then changed the type and things worked.  However, if I used .[Date], hierarchy type, it would say my moving average measure was (Blank) in the KPI visual.  I checked the dates using a table tile and it was showing dates in the future, yet when I look at the data directly there were no future dates.  This is historical data so there should be no future dates.  Yet after hours of fumbling around, I discovered that removing the .[Date] from the end of my dates column, the problem was corrected.  I thought .[Date] only collected the date (for example if it was a DateTime, then only output the date). However it appears to rather have a different purpose, more functionality than returning the date, or it has a bug.  My problem is solved, but just wanted to bring this up in case it causes problems for someone else as well.  If someone wiser than I know what is happening, by all means, let me know.