user: Question: What was the date of the Discus throw for Bulgaria?
Columns: ['Event', 'Record', 'Athlete', 'Nationality', 'Date']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['100 m', '10.72 (-0.3m/s)', 'Shelly-Ann Fraser-Pryce', 'Jamaica', '6 September 2013']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Nationality" = 'Bulgaria' AND "Event" = 'Discus throw';