CREATE TABLE table_21552 ("Team" CLOB, "Outgoing manager" CLOB, "Manner of departure" CLOB, "Date of vacancy" CLOB, "Replaced by" CLOB, "Date of appointment" CLOB, "Position in table" CLOB)

Name the date of appointment for petrik sander
SELECT "Date of appointment" FROM table_21552 WHERE "Replaced by" = 'Petrik Sander'
SELECT "Date of appointment" FROM "table_21552" WHERE "Replaced by" = 'Petrik Sander'