CREATE TABLE table_30997 ("Episode" FLOAT, "Date" TEXT, "Official rating 4+" TEXT, "Share 4+" TEXT, "Official rating 16-39" TEXT, "Share 16-39" TEXT)

When did the official rating 4+ reach 4 633 925?
SELECT "Date" FROM table_30997 WHERE "Official rating 4+" = '4 633 925'
SELECT "Date" FROM "table_30997" WHERE "Official rating 4+" = '4 633 925'