Adding Calculations in a custom report

I have been asked to create a SLA report that calculates the amount of time spent on each request, and how much time over or under the SLA each request was, in addition to the average time spent per request, and the Minimum and Maximum time spent on each request by tech. How can I add calculation to a custom report?

I have tried doing this through Crystal Reports but the date/time fileds (i.e.CreatedTIme) display as a large number, not any date/time format I am Familiar with.

Anyone have any ideas?

Report needs to include WO ID, TItle, Priority, SLA, Created TIme, Responded Time, Completed Time, TimeSpent, over/under SLA, ave time spent, minimum time spent, maximum time spent.