user: Question: What is the date of vacancy of team FC Bayern Munich, which had a date of appointment on 27 April 2009?
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: ['Bayer 04 Leverkusen', 'Michael Skibbe', 'Sacked', '30 June 2008[ citation needed ]', 'Bruno Labbadia', '1 July 2008[ citation needed ]', 'Pre-season']
SQL:

assistant: SELECT "Date of vacancy" FROM "Table" WHERE "Team" = 'FC Bayern Munich' AND "Date of appointment" = '27 April 2009';