How do I subtract two columns of data in sas and use that data to create a new variable? Also I am dealing with time data.

It is a simple question or I didn't get your question.
If you wanted to create difference of two columns, use data step. and create new variable as the difference of two coulmns.

In case you want to find the difference between two date variables(time data) then you should use INTCK() function.

Also check for INTNX() to calculate the difference of a date variable for fixed number of intervals.

Mahi..