The Arizona sentinel., 1886-06-05
EASTER CURIOSITIES.
How Order Is Brought Out of the Appar-
 ent Chaos of the Calendar.

How Order Is Brought Out of the Appar-
 ent Chaos of the Calendar.
 A paragraph has been going the rounds of the newspapers stating that Easter in 1886 fell on April 25, and that this had not occurred before since 1734, and would not happen again until 1943. This paragraph is useful only so far as it serves to draw attention to the rarity of the occurrence of Easter on any given day, but, unfortunately 1t con tains an erroneous statement, for Easter has occurred on April % since 1734- namely, in 1791. However, the subject itself is worthy of attention, since it seems admirably to illustrate some of the curious features of the calendar and to show how order is brought out of ap- parent chaos, for there are many seem- ingly discordant and inharmonious ele- ments entering into the problem of de- terming certain dates, which, after long periods, are found to blend and har- monize with mathematical precision.
 Every one knows that Easter is the Sunday following the first full moon oc- curing after March 21, and since this moon may fall on any day between the 21st of March and the Doth of April, it is apparent that the chances of its falling on any given day are very remote. If the question of weekday were ignored and only the day of the month were taken into account, then, according to the well-known meteorlc cycle, Easter would fall on the same day once in nine teen years with great regularity, for the error in this cycle is very small, as is shown by the following:
 Days. Hrs Min. l35 lunations require. ............6,939 l6 31
 19 tropical years ...69S9 IA 2i
 The Church rule for determining Easter is based upon this cycle, conse- quentlv if we make list ot the dates on which the Paschal full moon occurs, we shall find no two dates to be the same for nineteen successive years, but the twentieth will occur on the same day of the month with the first, when the whole series will be repeated. However, it is not with the day of the month so much as with the day of the week that we have to deal, and here is where the difficulty comes in, and the rarity of securing an agreement of the day of the week and the day of the month. necessary in the case of Easter, is best illustrated by the following, the results of calculations based on Ferguson's lunar tables from 1734 down to the present year:
 In 1734 the first full moon after March 2t fell on Sunday, April IS, consequently the following Sunday, April 9, was Easter Sunday. Nine teen years afterwards, in 1752, the first full moon after March 21 again fell on April IS, but this time April IS, instead of being Sunday, was Wednesday, and was the 22d instead of the 25th. Again after nineteen years, in 1772, we find similar dates, but April Is this year oc- cured on Friday, and the following Sunday was the 20th. In 1791 the Pas chal full moon fell on Monday, April 19, and Easter consequently fell on the 25th, as it did in 1886. There figures seem to indicate the occurrence of Easter on any named date at regular inter vals of three meteoric cycles of once every fifty-seven years, and such would undoubtedly be the case were it not for the fact that the question of leap-years enters into the problem. Between 1734 and 1791 leap years occurred regularly every four years, but after 1791 there was a period of eight years when none occurred; 1796 was leap year and then there was no other until 1894, the de- cree of Pope Gregory having reduced the year 1900 to 365 days. In con- sequence of this, at the end of fifty-seven years following 1791, in 1S4S, when Easter should have fallen on April 25, it fell one day short, on April "A. In 1867, nineteen years after 1S4S, the Paschal full moon fell on April IS, which was Thursday, and the following Sunday was the 21st. In this year the Paschal full moon falls on Sunday, April Is and Easter on April 25, and then after the lapse of fifty-seven years, namely, in 1943, it will fall on the same day again.-St Louis Globe Democrat.