Concurrence is the conjunction of two offices which succeed each other, so that the question arises to which of the two are the Vespers of the day to be assigned. The origin of this conjunction of feasts was by some old writers traced to the Mosaic law in which the festivals, began in the evening, and they quote "from evening until evening you shall celebrate your sabbaths" (Leviticus, xxii. 32). The effect of concurrence may be that the whole vespers may belong to the feast of the day or may be said entirely from, the feast of the following day; or it may be that the psalms and antiphons belong to the preceding festival and the rest of the office be from the succeeding feast. The General Rubrics, Title XI, must be read now in conjunction with Titles IV., V., and VI. of the Additiones et Variationes ad norman Bullae "Divino Afflatu". The rules for concurrence are given in Table III. of the Tres Tabellae inserted in the new Breviary (S.C.R., 23 January, 1912). These tables supersede the tables given in the old editions of the Breviary. The first of these two tables shows which office is to be said, if more than one feast occur on the same day, whether perpetually or accidentally. The second table is a guide to concurrence—i.e., whether the first vespers of the following feast is to be said entirely without reference to the preceding feast, or if second vespers of the preceding feast is to be said entire, without reference to the following; or, again, first vespers of the following with commemoration of the preceding, or second vespers of the preceding with commemoration of the following, or vespers of the more noble feast with commemoration of the other—any of these may be the liturgical order to follow, and the Tabella makes things clear.

The "tables" are to be used thus:—Opening the Breviary at the I Tabella, "Si occurrat eodem die," first find the number marked in that square in which the two feasts in question meet, and then read the direction printed, in column on same page to left-hand side, bearing the same number. For example: the question is about the occurrence of a Sunday of the first class and a Double of the first class. Double of the first class stands first word of page, and Sunday of first class will be found in column beneath the rows of figures. Now the square in which straight lines drawn from double of first class and Sunday of first class meet bears the number 6, and reference to number 6 in column of directions found on same page gives the rule, "Officium de 2, Translatio de I," that is, the office must be of the Sunday of first class and the double of the first class must be transferred according to the rubrics. When in these brief directive notes, (1-8), mention is made of the "first or the preceding," the reference is made to feast or office printed in the upper part of the Table, e.g., Double of first class. Reference to "the second" or "following" refers to feast printed in the lower section of the Table. Where O stands in a square in the Tabella it signifies that there can be no occurrence or concurrence between feasts whose "lines" meet in that square. These two tables are very ingeniously arranged. The lists, given in the Breviary following these tables, give the lists of greater Sundays and Ferias, privileged vigils, doubles of first and second class and greater doubles, and tell whether feasts are primary or secondary.