What are the guidelines (hour or approximate time of day) for when “Sunday” begins and ends with regard to 1) weekly mass obligation 2) refraining from servile work 3) easing of Lenten penance 4) partaking of the 2nd and final allowed Eucharist for an individual that day?
The answer to this quesiton is not perfectly clear.
The Code of Canon Law states:
Can. 1248 §1. A person who assists at a Mass celebrated anywhere in a Catholic rite either on the feast day itself or in the evening of the preceding day satisfies the obligation of participating in the Mass.
In consulting “The New Commentary on the Code of Canon Law”, commissioned by the Canon Law Society of America, and “The Canon Law: Letter and Spirit”, by the Canon Law Society of Great Britain and Ireland, both commentaries agree that the holy day itself (Sunday being the primary holiday) means from midnight at the beginning of the day to midnight which ends the day.
But the two commentaries disagree on what is meant by “the evening of the previous day”. The American Commentary states,
“Evening” should be understood as anytime from 4:00 P.M. onward."
The British commentary says,
“It is the firm view of this commentary that the evening of the previous day begins at midday (12 noon) on the day itself.”
So there is some confusion about this. The Pope is the ultimate interpretor of Canon Law, so unless and until the Pope interprets this for us, this will still be up open discussion.