CREATE TABLE table_77358 ("Name" TEXT, "Birth" TEXT, "Marriage" TEXT, "Became Dauphine" TEXT, "Ceased to be Dauphine" TEXT, "Death" TEXT, "Husband" TEXT)

when was the marriage when became dauphine is 31 august 1412?
SELECT "Marriage" FROM table_77358 WHERE "Became Dauphine" = '31 august 1412'
SELECT "Marriage" FROM "table_77358" WHERE "Became Dauphine" = '31 august 1412'