Q. 1. If I go to Holy Mass on Saturday night, does that attendance fulfill my Sunday Obligation to attend Holy Mass as required by the First Precept of the Church?
A. 1. Yes, it does. Church Canon Law # 1248 §1 states: "The obligation of assisting at Mass is satisfied wherever Mass is celebrated in a Catholic Rite either on a holyday itself or on the evening of the previous day."
For the Holy Mass to considered as the fulfillment of one's Sunday or holiday obligation, it must be a celebration of the liturgy (prayers, readings, Gospel) of the Sunday or holiday of the following day.
Q. 2. What does the Canon Law mean by "on the evening of the previous day?" When does the evening being? Is it at 7:00 P.M. or what?
A. 2. The Church has never defined when the evening begins. Some Bishops have proclaimed the validity of the Sunday Obligation begins at a certain hour on the previous day. For example, one Bishop proclaimed that the 3:00 p.m. Mass on the previous day fulfills the Sunday obligation. This is a clear abuse of a Bishop's authority since the "afternoon" is certainly not the "evening."
Most persons who work, they do so until 5:00 P.M. which is considered the end of the afternoon. Most person start their everning meal between 4:00 P.M. and 6:00 P.M. Therefore, it would be logical to say that their evening begins after they have completed that meal.
When the Vatican celebrates Sunday Masses on the previous evening, it is at 5:00 P.M.
Regarding one's attendance at a Holy Mass that begins at 5:00 P.M. or later on the previous day, it would be fair to say that such an attendance at Holy Mass, providing it includes the Sunday liturgy, fulfills one's Sunday obligation of attending Holy Mass. Anything earlier is very questionable!
It should be noted that most companies consider 6:00 P.M. as the beginning of the evening. Anything earlier than that would be considered the afternoon.
Q. 3. If I go to Holy Mass on Saturday night instead of Sunday, how does that affect my Sunday obligation of rest?
A. 3. Church Canon Law # 1247 states: "On Sundays and other holydays of obligation, the faithful are obliged to assist at Mass. They are also to abstain from such work or business that would inhibit the worship to be given to God, the joy proper to the Lord's Day, or the due relaxation of mind and body."
Attending Holy Mass on Saturday night versus Sunday does not change one's obligation to asbstain from shopping on Sundays and holydays and to rest on such days. That means faithful Catholics should not be going to shop on Sunday when such can be done on Saturdays. On Sunday, they should be resting and enjoying the day with their family and friends, doing some spiritual reading, reflection, meditation, enjoying the beauties of God's creations.