Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What date did the Chicago Bears beat the Green bay Packers 31-20?

### Inputs:
table_name: table, columns: ['Year', 'Date', 'Winner', 'Result', 'Loser', 'Attendance', 'Location']

### Response:
SELECT Date FROM table WHERE Loser = green bay packers AND Location = green bay