"Inter Gravissimas" by Pope Gregory XIII (translated into English)

Bishop Gregory, servant of the servants of God:—

For the perpetual remembrance of this matter:—

 

Amongst the most serious tasks of our pastoral office, not the least of them is to see to it that the affairs which the holy Council of Trent reserved to the Apostolic See are conducted, with God's help, to a desirable conclusion.

When the fathers of the said Council added to their outstanding considerations the care of the breviary, they were prevented by lack of time, and indeed by decree of the same Council they referred the whole matter to the authority and judgement of the Roman Pope.

There are two principal parts in the breviary. One comprises the prayers and divine praises to be offered on feast days and ordinary days; and the other relates to the annual recurrence of Easter and the feasts that depend on it, to be measured by the movement of the sun and moon.

Pius V, our predecessor, of happy memory, completed and brought into force what had to be done about the one part.

But the other part, which requires first a legitimate restoration of the calendar, could not be completed up to now, even though that was attempted on many occasions over a long period by our pontifical predecessors. That was because previous proposals for amending the calendar, put forward by experts in celestial motions, all involved great and nearly inextricable difficulties, and they would not have been of long-lasting effect, and also would not have maintained intact the ancient rites of the Church (of which care had to be taken above all).

While we too, confident of God's dispensation, were engaged in the task and considerations thus entrusted to us (unworthy though we may be), our dear son Antonio Lilio, doctor of arts and of medicine, brought to us a book previously written by his brother Aloysius. It appeared that the latter had devised a certain new cycle of epacts, adapted to a certain rule of the golden number, and an accommodation for every length of the solar year, showing that all the things that have fallen into disarray in the calendar can be restored on a consistent basis that will be everlasting, so that the calendar will not suffer any alteration again.

A few years ago we therefore circulated this new calendar-restoration proposal, in a small book, to Christian princes and to well-known universities, so that this matter, which is of common concern, might be brought to perfection by the advice of all. When they responded with agreement, as we had greatly hoped, we were led by their agreement to invite the greatest experts in such matters to the Holy City for the amendment of the calendar; they had already long since been selected from the principal Christian nations of the world.

When these experts had applied themselves to the matter with much time, diligence and study into the night, and had searched out cycles, both ancient and modern, from all sources, and discussed them and most carefully evaluated them, they chose, by their own judgment and that of learned men who wrote about the matter, in preference to other things, this cycle of epacts, to which they have also added some things which are seen after careful circumspection to be needed for perfecting the calendar.

Therefore, considering that for the proper celebration of the feast of Easter, according to the holy fathers and Roman pontiffs of ancient time, especially Pius I and Victor I, as also that great ecumenical Council of Nicaea among others, three necessary things have to be set together and established:

 

    first, correct placement of the vernal equinox;

    next, correct placement of the fourteenth day of the moon in the first month, which either occurs on the day of the equinox itself or is the next to follow after;

    and lastly, the first Sunday which follows that same fourteenth day of the moon;

 

we have arranged—

 

    not only to restore the vernal equinox to its original place from which it has already receded by about ten days since the Council of Nicaea,

    and to replace the paschal fourteenth day of the moon back into its place from which it is currently distant by four days and more,

    but also for a method and a rule to be handed down, for preventing the equinox and the fourteenth day of the moon from ever again in future being moved away from their proper places.

 

Therefore, in order to restore the vernal equinox, which was placed by the fathers of the Council of Nicaea at the twelfth day before the Kalends of April, and to return it to that same place, we direct and ordain:

 

    that ten days shall be removed from the month of October of the year 1582, from the third day before the Nones  up to the day before the Ides, inclusive;

    and that the day which follows the feast of St Francis (as usually celebrated on the fourth day before the Nones) shall be called the Ides of October, and on it shall be celebrated the feast of saints Dionysius, Rusticus and Eleutherius, martyrs, with commemoration of St Mark, pope and confessor, and of Saints Sergius, Bacchus, Marcellus and Apuleius, martyrs.

    On the seventeenth day before the Kalends of November, which shall be the day next following, there shall be celebrated the feast of St Callistus, pope and martyr.

    Then on the sixteenth day before the Kalends of November, the Dominical Letter shall be changed from G to C, and the office and Mass shall be those of the 18th Sunday after Pentecost.

    Finally, the fifteenth day before the Kalends of November shall be the feast of St Luke, evangelist;

    after which, the remaining feast days shall take place successively, as they are described in the calendar.

 

But in order that nobody suffers prejudice by this our subtraction of ten days, in connection with any annual or monthly payments, the judges in any controversies that may arise over this, shall by reason of the said subtraction add ten days to the due date for any such payment.

Next, so that the equinox will no longer recede in future from the twelfth day before the Kalends of April, we decree:

 

    that the bissextile day every fourth year shall continue, as the custom is now, except in centurial years, although these were always bissextiles before, and we wish the year 1600 to be bissextile as well;

    after that, however, the centurial years that follow shall not all be bissextiles, only every fourth centurial year shall be bissextile, thus the years 1700, 1800 and 1900 shall not be bissextile. But in the year 2000, the bissextile day shall be added in the usual way, with February containing 29 days;

    and then the same order of leaving out and adding the bissextile day shall be observed in each period of 400 years ever after.

 

Again, so that the fourteenth day of the paschal moon may be correctly found, and that the age of the moon may be truly announced to the faithful every day from the martyrology, according to the ancient custom of the Church, we decree:

 

    that the golden number is to be removed from the calendar and in its place is to be substituted a cycle of epacts, regulated (as we have said) by a certain rule of the golden number, to make sure that the new moon and the paschal fourteenth day of the moon will always retain their true places.

 

This is made manifestly clear in our explanation of the calendar, which also describes Paschal tables according to the ancient rite of the Church, from which the date of the most holy Pasch can more certainly and easily be found.

Finally, on account partly of the ten days removed from the month of October in the year 1582 (which ought properly to be called the year of correction) and on account partly of the three days fewer to be intercalated in each period of 400 years, it is necessary to interrupt the 28-year cycle of Dominical Letters as it has been used in the Roman Church up to now. We wish to be substituted in its place the cycle of 28 years as the same Lilio has adapted it to the rule of intercalation in centurial years and to every duration of the solar year; from which the Dominical Letter may be found in perpetuity as easily as before, with the benefit of the solar cycle as explained in the Canon that deals with this.

By this our decree, we therefore assert what is the customary right of the sovereign pontiff, and approve the calendar which has now by the immense grace of God towards his Church been corrected and completed, and we have ordered that it be printed and published at Rome in one with the martyrology.

But in order that each of them may be preserved intact and free from errors and mistakes throughout the world, we forbid all printers established in territories which are either directly or through intermediaries within our jurisdiction, and the printer to the holy Roman Church, from daring or presuming to print or publish the calendar or martyrology without our authorisation, either together or separately, or to profit from them in any way, under pain of loss of books and payment of 100 ducats of gold ipso facto to the Apostolic Chamber; and as for other printers, wherever they may be established, we prohibit them from daring or presuming to print or publish the calendar or martyrology without our licence, whether separately or together, under pain of excommunication latae sententiae and other penalties at our discretion.

On the other hand we entirely repeal and abolish the old calendar; and we wish all patriarchs, primates, archbishops, bishops, abbots, and others who preside over churches, to introduce the new calendar (to which also the martyrology has been adapted) for reciting divine offices and celebrating feasts in all their churches, monasteries, convents, orders, militias and dioceses, and to use it exclusively, for themselves and for all other presbyters and clergy both secular and regular, of either sex, along with all soldiers and all Christian faithful; the use of it shall commence after the ten days have been left out of the month of October in the year 1582. But for those who inhabit regions too far away for them to have notice of these letters from us before the time prescribed, they are permitted to make the change in the same month of October of the following year 1583, or the next, that is to say, when these our letters first arrive with them, in the manner indicated above and as will be more abundantly explained in our calendar of the year of correction.

We also, by virtue of the authority given to us by the Lord, exhort and ask of our dear son in Christ, Rudolph, illustrious king of the Romans and emperor-elect, as well as other kings, princes, and republics, and we recommend to those who pressed us to complete this so excellent work, also and especially for the sake of maintenance of concord between Christian nations in the celebration of feasts, both to adopt this our calendar for themselves, and to take care that all the peoples subject to them religiously accept it and scrupulously observe it.

As it may be difficult to distribute these letters to all Christian places in the world, we ordain that they be published and affixed to the doors of the basilica of the prince of apostles and of the apostolic chancellery, and at the entrance to the Campo dei Fiori; and we order the same undoubted faith to be accorded among all peoples and in all places, also to printed copies of these letters and of the volumes of calendar and martyrology, when signed by a notary public and sealed with the seal of an ecclesiastical dignitary, as the original letters would have in their entirety.

It is therefore entirely forbidden to any man to infringe these our precepts and decrees, mandates, statutes, will, approval, prohibition, sublation, abolition, exhortation and request, or to dare to bear witness or proceed against them. If nevertheless any presume to make such an attempt, they are to know that they will incur the indignation of almighty God and of the blessed apostles Peter and Paul.

 

Given at Tusculum, in the year of the incarnation of our Lord 1581, on the sixth day before the Kalends of March, and in the tenth year of our pontificate.