 No feast whatsoever could replace the celebration of these Sundays, with the sole exception of the feast of the Immaculate Conception.All other Sundays were of II class, and outranked feasts of II class, with the exception that feasts of the Lord, whether I or II class, which replaced the celebration of any II class Sunday on which they happened to fall.The 1955 reform of Pope Pius XII did not have this division of Sundays into classes.