The complete Rosary is composed of twenty decades. It is divided into four distinct parts, which may be said separately at different times of the day, the five Joyful Mysteries, the five Luminous Mysteries, the five Sorrowful Mysteries, the five Glorious Mysteries. If you say only five decades a day, it is customary to say the Joyful Mysteries on Monday and Saturday, the Luminous Mysteries on Thursday, the Sorrowful Mysteries on Tuesday and Friday, the Glorious Mysteries on Wednesday and Sunday.