CREATE TABLE table_37081 ("Date" TEXT, "Tournament" TEXT, "Winning score" TEXT, "Margin of victory" TEXT, "Runner ( s )  up" TEXT)

On what date was the winning score 20 (68-67-65-64=264)?
SELECT "Date" FROM table_37081 WHERE "Winning score" = '–20 (68-67-65-64=264)'
SELECT "Date" FROM "table_37081" WHERE "Winning score" = '–20 (68-67-65-64=264)'