user: Question: When was Kalin Olson listed as  the centerfold model?
Columns: ['Date', 'Cover model', 'Centerfold model', 'Interview subject', '20 Questions', 'Pictorials']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['1-97', 'Marilyn Monroe', 'Jami Ferrell', 'Whoopi Goldberg', 'Mike Judge', 'Marilyn Monroe']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Centerfold model" = 'Kalin Olson';