user: Question: What date was the circuit, Snetterton, when Riki Christodoulou had the fastest lap?
Columns: ['Circuit', 'Date', 'Pole Position', 'Fastest Lap', 'Winning driver', 'Winning team']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Brands Hatch', '29 March', 'Alexander Sims', 'Ryuji Yamamoto', 'Riki Christodoulou', 'Fortec Motorsport']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Circuit" = 'Snetterton' AND "Fastest Lap" = 'Riki Christodoulou';