Days between two dates columns in DirectQuery

ricgin, in the query editor, you should be able to substract two date columns by simply using the "-" operator. There's a ribbon operation for this: select the two columns, go to Add Column -> Time -> Substract.

The resultant column is of type Duration. When loaded into AS this will get converted to a bigint, which is accurate to 0.1ms. Then you can use simple math to extract the portion of this field. For example, to get to the total number of days:

Column = [TimeDifference] / 1E7 / 60 / 60 / 24