An apostolic letter on keeping the Lord's Day holy, given on Pentecost 1998 in preparation for the Great Jubilee. It gathers five names for Sunday and gives a chapter to each: Dies Domini, the day of the Lord as the day of creation; Dies Christi, the day of the risen Lord and of the gift of the Spirit; Dies Ecclesiae, the day of the eucharistic assembly, where the Sunday obligation is explained as the response of a people gathered by the Lord; Dies Hominis, the day of rest, joy, solidarity and works of mercy; and Dies Dierum, Sunday as the primordial feast that reveals the meaning of time.