ok after reviewing I think the line:

AND [Calendar Date] < DATEADD(hh, -9, @End_Date) -- excludes days when disconnected before hours

should be:

AND [Calendar Date] < DATEADD(hh, -8, @End_Date) --...

First of all, thanks for this; it is very close to what I needed as well. The issue i'm having though is it doesn't seem to count time from 8...