user: Question: Name the date for W 31-28
Columns: ['Week', 'Date', 'Opponent', 'Result', 'Game site', 'Record', 'Attendance']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'real']
Sample row: [1.0, 'September 2, 1979', 'San Diego Chargers', 'L 16-33', 'Kingdome', '0-1', 62887.0]
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Result" = 'W 31-28';