Whilst I was deriving a solution, June responded with a similar solution to mine involving a UNION query and a dummy table which is required for the query but not used
As I had already done it, you may as well have it as another solution.
This creates records in the format Dec 2018 & Jan 2018
Code:
SELECT DISTINCT Format(Date(),"mmm yyyy") AS MY FROM Table1;
UNION SELECT DISTINCT Format(DateAdd("m",1,Date()),"mmm yyyy") FROM Table1;
If possible use a reference Table1 with only one record. If so OMIT both of the DISTINCT