CREATE TABLE table_31595 ("Year" FLOAT, "Date" TEXT, "Event" TEXT, "Days" TEXT, "Stages" TEXT, "Acts" TEXT)

Tell me the date for acts of 6 bands and year larger than 1981 for monsters of rock
SELECT "Date" FROM table_31595 WHERE "Acts" = '6 bands' AND "Year" > '1981' AND "Event" = 'monsters of rock'
SELECT "Date" FROM "table_31595" WHERE "Acts" = '6 bands' AND "Event" = 'monsters of rock' AND "Year" > '1981'