Number of days between two dates

[Bjarne_Allerup]

Hi I do not understand why this will not work. I try to calculate number of dates between ArriveDate and DepartureDate

It looks like [Departure Date]-[Arrive Date] give me number of Hours, which I try to divide by 24 to get number of days.

But it says “Invalid operator”???

Thanks in advance
Bjarne Allerup