For purposes of gaining a plenary indulgence, when does the day start?

Question

According to Enchiridion Indulgentiarum, a plenary indulgence can normally be granted only once per day (Normae de Indulgentiis No. 18 - § 1) unless the believer is at the point of death (§ 2).

How is it determined when the next day starts for the purposes of gaining a new plenary indulgence? For example, if (this is an extreme example to illustrate my question) Bob gains a plenary indulgence at 11:59 PM on May 30, can he obtain another plenary indulgence at 12:01 AM on May 31 or does he have to wait until 11:59 PM on May 31 to get another? Similarly, if Bob gains a plenary indulgence at noon on May 30 and then takes a one hour flight westbound across the International Date Line to a place where it's already May 31, can he get another one immediately or does he have to wait 23 more hours?

Yes, I know, one can gain unlimited partial indulgences a day and an otherwise plenary indulgence which fails to meet all the criteria for its reception drops down to a partial one, so Bob's efforts would not be completely wasted, but I'm curious if this is discussed anywhere.

• Are days reckoned according to local law and custom (i.e. the civil time zone and calendar date)? This would mean, for example, that if the Ruritanian Parliament passes a law on January 1 at 7 AM making it immediately and legally January 2, Catholics in Ruritania can go out immediately and get another plenary indulgence even if they just got one an hour ago.
• Do days begin and end at astronomical midnight at the location where a person is currently present, without regard to local custom, law, or time zone designation?
• Are days reckoned per Old Testament practice as beginning at sunset rather than midnight, and one must wait until sunset to get another plenary indulgence, and it doesn't matter if sunset is one minute away or eleven hours and 59 minutes away?
• Does the granting of a plenary indulgence have a strict cool-down period of 24 hours as measured by a stopwatch?

If there is a more general (not explicitly tied to indulgences) teaching in Catholicism or Canon Law on the definition of "once per day" or "daily" that could reasonably be understood to apply to this situation, I would accept that as an answer.

For some background to this question, there are a fairly large number of posts on our sister site Mi Yodea (and in Judaism in general) on the exact nature of the beginning, ending, and succession of days and how civil time zone changes, rapid long-distance travel, the International Date Line, and even travel into space affects time-bound commandments that must be observed on a specific date or day of the week. I'm curious as to whether Catholicism has anything similar.

Answer 1

For purposes of gaining a plenary indulgence, when does the day start?

One can only gain one plenary indulgence per day. So far this is clearly stated by Rome. The only exception to this is when a person is near death and receives the Last Rites in which a plenary indulgence may be even if one has already gained a plenary indulgence that day!

Before going on this the next step, I would like to post the 7 mains norms involved in getting a plenary indulgence as stated from the Apostolic Penitentiary:

General Remarks On Indulgences

1. This is how an indulgence is defined in the Code of Canon Law (can. 992) and in the Catechism of the Catholic Church (n. 1471): "An indulgence is a remission before God of the temporal punishment due to sins whose guilt has already been forgiven, which the faithful Christian who is duly disposed gains under certain prescribed conditions through the action of the Church which, as the minister of redemption, dispenses and applies with authority the treasury of the satisfactions of Christ and the saints".

2. In general, the gaining of indulgences requires certain prescribed conditions (below, nn. 3, 4), and the performance of certain prescribed works (nn. 8, 9, 10 indicate those specific to the Holy Year).

3. To gain indulgences, whether plenary or partial, it is necessary that the faithful be in the state of grace at least at the time the indulgenced work is completed.

4. A plenary indulgence can be gained only once a day. In order to obtain it, the faithful must, in addition to being in the state of grace:

— have the interior disposition of complete detachment from sin, even venial sin; — have sacramentally confessed their sins; — receive the Holy Eucharist (it is certainly better to receive it while participating in Holy Mass, but for the indulgence only Holy Communion is required); — pray for the intentions of the Supreme Pontiff.

5. It is appropriate, but not necessary, that the sacramental Confession and especially Holy Communion and the prayer for the Pope's intentions take place on the same day that the indulgenced work is performed; but it is sufficient that these sacred rites and prayers be carried out within several days (about 20) before or after the indulgenced act. Prayer for the Pope's intentions is left to the choice of the faithful, but an "Our Father" and a "Hail Mary" are suggested. One sacramental Confession suffices for several plenary indulgences, but a separate Holy Communion and a separate prayer for the Holy Father's intentions are required for each plenary indulgence.

6. For the sake of those legitimately impeded, confessors can commute both the work prescribed and the conditions required (except, obviously, detachment from even venial sin).

7. Indulgences can always be applied either to oneself or to the souls of the deceased, but they cannot be applied to other persons living on earth.

The Gift of the Indulgence

As stated from the above article one can only receive a plenary indulgence once a day. As far as partial indulgences are concerned there is no limit.

Rome has not thought it necessary to explain or define what is meant by a day!

Obviously, for the Church the day refers to to the modern conception as to what is the 24 hour period of a modern day, that is to say from 12:00 A.M. to 11:59:59 P.M.

That much is clearly. One can gain the plenary indulgence anytime within this time frame!

Even our Lenten Observe starts at midnight of Ash Wednesday!

The Church, as we know, does not follow the Jewish reckoning of when the day starts and she follows the Gregorian Calendar instead of Julian Calendar. The Hebrew Calendar or Jewish Calendar is not followed either.

Nor is the Jewish manner of how to reckon when the day begins followed either. Their day starts at sundown, whereas the Church day starts at midnight. The is the basis in which the whole of her Liturgical Year is fixed...