Where permission has been granted by the Apostolic See to fulfill the Sunday obligation on the preceding Saturday evening, pastors should explain the meaning of this permission carefully to the faithful and should ensure that the significance of Sunday is not thereby obscured. The purpose of this concession is in fact to enable the Christians of today to celebrate more easily the day of the resurrection of the Lord.
All concessions and contrary customs notwithstanding, when celebrated on Saturday this Mass may be celebrated only in the evening, at times determined by the local Ordinary.
In these cases the Mass celebrated is that assigned in the calendar to Sunday, the homily and the prayer of the faithful are not to be omitted.
What has been said above is equally valid for the Mass on holy days of obligation which for the same reason has been transferred to the preceding evening.