That one line should be:
var days = +getField("AddedDays").value;
Also, check to make sure that the field calculation order is correct.
So, I think I've found my issue which still has me confused. For the purpose of simplification, I didn't actually explain my full scenario. The "InitialDate" field is actually a calculated field itself from another field called "DateRequest". So, the formula is trying to use a field that is a calculated field in and of itself. Is there a way to order it so that all fields are immediately updated (like in a 'mouse up' event)?
Yes, you need to correct the field calculation order as mentioned earlier. Exactly how you do this depends on which version of Acrobat you're using.
While you're in form editing mode, select:
Acrobat 9: Forms > Edit Fields > Set Field Calculation Order
Acrobat 10: Tasks > Other Tasks > Edit Fields > Set Field Calculation Order
Acrobat 11: Tasks > Other Tasks > Set Field Calculation Order
Acrobat DC: More (button in right-hand panel) > Set Field Calculation Order
Field Calculation Order did the trick and it is working great now. THANK YOU!!!!