Dbms_advanced_rewrite to return a new date

Question

Is there a way to offset the database date by a given amount of months/days/years so that when the sysdate is queried, it returns a date which equals the current date+the offset? This has to be done without changing the server's OS date.
I'm trying to achieve it using 'dbms_advanced_rewrite' but getting the following error.
begin
sys.dbms_advanced_rewrite.declare_rewrite_equivalence (
'new_query',
'select sysdate as tdt from dual',
'select sysdate+180 as tdt from dual',
false);
end;
2 3 4 5 6 7 8 begin
ERROR at line 1:
ORA-30353: expression not supported for query rewrite
ORA-06512: at "SYS.DBMS_ADVANCED_REWRITE", line 29
ORA-06512: at "SYS.DBMS_ADVANCED_REWRITE", line 185
ORA-06512: at line 2
any help would be much appreciated.
thanks

Answer 1

I don't know why the error is occurring. I've worked with DBMS_ADVANCED_QUERY_REWRITE a little, enough to find out that you can alter result sets using it. My exercise was to get a 'Y' instead of an 'X' from DUAL, and the exercise was successful. I didn't try using SYSDATE with it.
What happens if you use ROWNUM (another pseudocolumn) instead of SYSDATE? What happens if you use a literal or database column value?
Can you approach the problem from a different way? Specifically, could you create a view with the query you want and then alter the value in the view as needed, having your user use the view instead of a straight query. Not as elegant, but it should work