This is exactly the same issue that I am facing here:
https://bobj-board.org/t/dynamic-date/250377
Are you using the JCO connection? In my post many people suggested a form of database function such as Current Date or Get Date()
I have been looking at this again today and I think it has something to do with the database driver. comparing the .prm files for various drivers there are definitions for database functions. The SAP JCO prm for R/3 is very small.
When you come to add the database function to your “where” clause in the filter, I am limited to “numeric Functions” there is no subset of DateTime functions and no definition for “current Date”
This screen shot shows the database functions on the SAP R3 connection vs a SQL based connection.
Hopefully this defines the problem better & someone may assist in resolving the problem for both of us!
John
IknoNothing 
(BOB member since 2017-11-30)