107 The liturgical year is to be revised so that the traditional customs and discipline of the sacred seasons shall be preserved or restored to suit the conditions of modern times; their specific character is to be retained, so that they duly nourish the piety of the faithful who celebrate the mysteries of Christian redemption, and above all the paschal mystery. If certain adaptations are considered necessary on account of local conditions, they are to be made in accordance with the provisions of Art. 39 and 40.
Source: Sacrosanctum Concilium (Vatican.va)