CREATE TABLE table_41930 ("Week" FLOAT, "Date" TEXT, "Opponent" TEXT, "Result" TEXT, "Attendance" TEXT)

On what date did the Bills play the Houston Oilers before week 12?
SELECT "Date" FROM table_41930 WHERE "Week" < '12' AND "Opponent" = 'houston oilers'
SELECT "Date" FROM "table_41930" WHERE "Opponent" = 'houston oilers' AND "Week" < '12'