CREATE TABLE table_19359427_6 (date_of_appointment VARCHAR2, position_in_table VARCHAR2)

When was the new manager of the team on 21st position appointed?
SELECT date_of_appointment FROM table_19359427_6 WHERE position_in_table = "21st"
SELECT "date_of_appointment" FROM "table_19359427_6" WHERE "21st" = "position_in_table"