CREATE TABLE table_40791 ("Date" TEXT, "Tournament" TEXT, "Winning score" TEXT, "Margin of victory" TEXT, "Runner ( s ) -up" TEXT)

On what date was the tournament played that eneded with a winning score of +6 (74-71-70-71=286) and margin of victory of 2 strokes, and with Arnold palmer as the runner-up?
SELECT "Date" FROM table_40791 WHERE "Runner(s)-up" = 'arnold palmer' AND "Margin of victory" = '2 strokes' AND "Winning score" = '+6 (74-71-70-71=286)'
SELECT "Date" FROM "table_40791" WHERE "Margin of victory" = '2 strokes' AND "Runner(s)-up" = 'arnold palmer' AND "Winning score" = '+6 (74-71-70-71=286)'