Calculating hours for each dates between 2 date columns

Hello AlienBI 

Try this DAX Measure

OnRent =
VAR tmpOnRent =
ADDCOLUMNS (
'DemandPlotterRA+RES',
"Pickup", 'DemandPlotterRA+RES'[Pick up date],
"Dropoff", 'DemandPlotterRA+RES'[Drop off date]
)
VAR tmpTable =
ADDCOLUMNS (
FILTER (
GENERATE ( tmpOnRent, 'Calendar' ),
[Date] >= INT ( [Pickup] )
&& [Date] <= INT ( [Dropoff] )
),
"RentalHours",
VAR StartOfDay = [Date] // midnight
VAR EndOfDay = [Date] + 1 // next midnight
VAR StartTime = MAX ( [Pickup], StartOfDay )
VAR EndTime = MIN ( [Dropoff], EndOfDay )
RETURN
DIVIDE ( DATEDIFF ( StartTime, EndTime, MINUTE ), 60, 24 )
)
RETURN
SUMX ( tmpTable, [RentalHours] / 24 )