CREATE TABLE table_7642 ("Date" TEXT, "Tournament" TEXT, "Winning score" TEXT, "To par" TEXT, "Margin of victory" TEXT)

On what Date is the Winning Score 71-69-68-70=278?
SELECT "Date" FROM table_7642 WHERE "Winning score" = '71-69-68-70=278'
SELECT "Date" FROM "table_7642" WHERE "Winning score" = '71-69-68-70=278'