Due date calculates an incorrect date.

Currently when we rent our space, we require all fees be paid 2 weeks prior to the event date.  I have attempted this using the form calculation, but the date it returns is not accurate.  For example, with an event date of 3-22-2019 it returns a date of 11-30-1899.  

Here is how I attempted it....

You are using the subtract sign as "String". Please check my screencast below on how to change the String to a number.

Let us know if you have any questions or if you need further assistance.