CREATE TABLE table_31803 ("Year" FLOAT, "Date" CLOB, "Event" CLOB, "Days" CLOB, "Stages" CLOB, "Acts" CLOB)

When is the Monsters of Rock show with 12 bands?
SELECT "Date" FROM table_31803 WHERE "Event" = 'monsters of rock' AND "Acts" = '12 bands'
SELECT "Date" FROM "table_31803" WHERE "Acts" = '12 bands' AND "Event" = 'monsters of rock'