Calculating how many hours between one date and another

[Guest]

I have four cells in a spreadsheet

start date
start time
end date
end time

I need to calculate in hours the difference between the start date and time
and the end date and time. This is probably quite easy, but I can't find the
way to do it. Unfortunately the cells have to remain seperate

 

[Guest]

Subtract as normal (start date + start time - end date - end time) and
multiply the result by 24. You'll probably have to format the resulting
number.

 

[Guest]

=(startdate+starttime)-(enddate+endtime) and format the result something like
hhh.

 

[Niek Otten]

Make the format [h] instead