user: Question: what is the date of vacancy when the manner of departure is Contract terminated, the position in table is 23rd and the date of appointment is 31 December 2008?
Columns: ['Team', 'Outgoing manager', 'Manner of departure', 'Date of vacancy', 'Replaced by', 'Date of appointment', 'Position in table']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Bournemouth', 'Kevin Bond', 'Contract terminated', '1 September 2008', 'Jimmy Quinn', '2 September 2008', '23rd']
SQL:

assistant: SELECT "Date of vacancy" FROM "Table" WHERE "Manner of departure" = 'Contract terminated' AND "Position in table" = '23rd' AND "Date of appointment" = '31 December 2008';