user: Question: What are the dates of the outgoing manager Colin Hendry does appointments? 
Columns: ['Team', 'Outgoing manager', 'Manner of departure', 'Date of vacancy', 'Replaced by', 'Date of appointment']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Clyde', 'Joe Miller', 'Mutual consent', '25 May', 'Colin Hendry', '11 June']
SQL:

assistant: SELECT "Date of appointment" FROM "Table" WHERE "Outgoing manager" = 'Colin Hendry';