CREATE TABLE table_53946 ("Year" FLOAT, "Date" TEXT, "Winner" TEXT, "Result" TEXT, "Loser" TEXT, "Attendance" FLOAT, "Location" TEXT)

What date did the Chicago Bears beat the Green bay Packers 31-20?
SELECT "Date" FROM table_53946 WHERE "Loser" = 'green bay packers' AND "Location" = 'green bay'
SELECT "Date" FROM "table_53946" WHERE "Location" = 'green bay' AND "Loser" = 'green bay packers'