It depends on how much flexibility/control you have on the database server
DELETE FROM <DBNAME>.<SCHEMANAME>.<TABLENAME>
WHERE DATEDIFF(day,<DATETIMECOLUMNNAME>,GETDATE()) >= 30
You can schedule a job to execute the above t-sql statement once per day every morning [OR] you can execute this as a startup script in your web-application (or whichever the app may be) tied to an even such as first login or session startup or something similar (not ideal though) In case of latter, you better maintain a flag somewhere to check if the statement is ever executed (successfully) for that day.
Regards
Vasu
Regards, Sreenivas (Vasu) Chaparala
ps:Unless a question, this is an attempt to provide guidance. Turning this into a solution, if required, is ones own responsibility. Expecting the entire solution as-is is inappropriate for any professional.