Dwayland,
If you are using SQL*Server you can insert records with a date column of the current day (in SQL*Server Getdate() function).
When you check what you want to delete Use the function DATEDIFF(day, insertdate, GETDATE()) to check if the result is greater then 30 in a having clause.
i.e.
DELETE TABLE
Having DATEDIFF(day, insertdate, GETDATE()) > 30
Hope this works for you