I am wondering if anyone can send me an example of a date calcuation.
I am trying to calculate from 21 days from an enrollment date. How would I create this in an expression?
I believe the function you're looking for is _add_days(...) The exact parameters are in the report studio user guide I believe.
As Kaevne mentioned, you can use the _add_days( date1, int) but you should use - int for subtraction.
So, if you want to subtract 21 days from any given date, the calculation should be something like
_add_days( enrollment_date, -21)
Hope this will solve your problem.