Like in the other
thread you had, you need to convert to Date using the to_number() or to_char() data type and do your math there. These functions allow you to specify the format or part of the Date/Time that you want to be able to do your calculations. Remember though, that after you convert your dates, subtraction will loop around 100, and not at 24 or 60.
I think
you should visit
Ask Tom and do a search, I guarantee you will find an answer there that is the best answer.
Mark