Delete records older than N days, hours or minutes in SQL Server

To delete records from a table that have a datetime value in Date_column older than 30 days use this query:

USE Database_name;
DELETE FROM Table_name
WHERE Date_column < GETDATE() - 30

...or this:

USE Database_name;
DELETE FROM Table_name
WHERE Date_column < DATEADD(dd,-30,GETDATE())

To delete records from a table that have a datetime value in Date_column older than 12 hours:

USE Database_name;
DELETE FROM Table_name
WHERE Date_column < DATEADD(hh,-12,GETDATE())

To delete records from a table that have a datetime value in Date_column older than 15 minutes:

USE Database_name;
DELETE FROM Table_name
WHERE Date_column < DATEADD(mi,-15,GETDATE())