If it was evident that the month Nisan would terminate before the vernal equinox—its beginning and middle had to precede the equinox, as well as the quarta decima lunæ—and if the barley was not in ear by the 14th, then it was considered the discrepancy had to be set right. This was done by prolonging the last month of the expiring year, Adar, for twenty-nine days longer than usual. In other words, an additional month was added to the year, designated merely as Veadar. This was the intercalary month. This, happening thrice in eight years, brought the lunar and solar years into agreement by a very simple expedient. The equinox could be controlled by help of the Zodiac, for, on the 20th March, the sun enters Aries, and, on the 23rd September, Libra.
Had the Jews followed out this method scientifically, i.e., had the introduction of the intercalary months followed fixed laws and been ruled by astronomical observations and calculations, then, though still difficult, it would have been possible to make the Jewish Calendar synchronise with others. But the introduction of these additional days was, so to speak, arbitrary and dependent upon the good pleasure of the priests. Thus we can never say for certain that such and such a year was a leap year with the Jews, and accordingly no date in the past can with certainty be made to synchronise with a date in the Julian or any other Calendar.[106]
Until their dispersion after the Jewish war in A.D. 70, and even much later, the Jews reckoned their new moons and leap years, and also the beginning of each year, not by strictly astronomical data, but by the method just described. The rule was that the month began with the day on the evening of which the new moon first became visible, and also that the passover should be kept when the sun was in Aries.[107] Maimonides, agreeing with what we have said above, informs us that a second Adar was interposed if the vernal equinox fell on the 16th Nisan or later. But it would be a great mistake to think that a scientifically accurate system, founded on these principles, was employed for calculating the new moons and leap years, such as would make it possible to bring the dates of the Jewish year into certain correspondence with the Julian Calendar. Still we must not think no attempts were made to reduce the Calendar to order on the basis of some cyclic system, but the caprice of the Sanhedrin always succeeded in rendering these attempts unavailing. Ideler (i. 512) shows how the new moons were treated, and Maimonides tells us that the Sanhedrin was influenced by many considerations in the choice of leap years. The Talmud preserves a remarkable letter written by Rabbi Gamaliel, the teacher of St Paul, to the Jews of Babylon and Media, which may appositely be quoted here. “We herewith inform you that we, in conjunction with our colleagues, have deemed it necessary to add thirty days to the year, since the doves (to be offered in sacrifice) are still too tender, and the lambs (for the passover) too young, and the time of Abib (the barley harvest) has not arrived.”
This passage may well serve as a warning to those who, whenever they find a fixed date in ancient Jewish writings, forthwith, with the aid of lunar tables, transpose it into a date according to the Julian method of reckoning, and possibly flatter themselves they have found a fixed point which will form a basis for further calculations.
In consequence of what we have said, it seems natural that Jewish converts to Christianity in apostolic times in the East should have fixed the date of Easter by Jewish methods, without departing, in this respect, from Jewish customs, especially as they formed the majority in the Church. This was all the more natural since in Syria and in many parts of Asia Minor, a Calendar drawn up on similar principles to the Semitic, was in use alongside the Greek (i.e. Roman) Calendar. This custom, however, although retained by the Quartodecimans, was never widespread, and did not long survive. The principal consideration, which demanded a departure from Jewish methods, was, that from the Christian point of view, the Resurrection, and not the day of Christ’s death, formed the chief feature of the commemoration; the latter, although a day to be had in remembrance, could not well be kept as a joyous festival. But the Resurrection took place on the Sunday after the 15th Nisan, and so this Sunday came to be the chief day of the Christians’ feast.
Through the gradual spread of Christianity in non-Semitic lands in the West, the necessity must soon have arisen of fixing the day of the Resurrection by the Julian Calendar, and of deciding according to it the day on which Easter had to be celebrated. But, as we have said, it is very difficult to transfer a date from the Jewish to the Julian Calendar, and, in most cases, quite impossible when the date is that of an event already long past.
Let us apply all this to the point in question.
If it was asked, “On what day did Christ die?” the answer was, “On the 15th Nisan.” But if it was asked again, “On which day of the Roman Calendar does the 15th Nisan fall?” the reply must be, “Who can tell? In one year it may fall in March, in another in April; sometimes on one day of our Calendar, sometimes on another.”
The reply, “On the 15th Nisan,” conveyed nothing either to the Romans or to the Egyptians; it was intelligible to the Semites alone. Thus, where the Semitic Calendar was not understood, it was necessary to fix the day by some other method. In the choice of methods, the Church of Alexandria, and, most of all, the Church of Rome, took the lead. The simplest plan would have been to discover on which day of March or April the 15th Nisan had fallen in the year of Christ’s death, i.e. 782 U.C. But it was impossible to do this with certainty after a few decades had elapsed. Another starting-point had to be sought, and this was naturally given by the spring full moon, i.e. the full moon nearest to the vernal equinox, for the 15th Nisan must fall either on this full moon or thereabouts. Thus in Rome and Alexandria, all the principles which are in force at the present day were gradually adopted, i.e. Easter is to be celebrated on the Sunday after the full moon following the vernal equinox. There is evidence that this rule for determining the date of Easter was followed in Rome from the time of Pope Sixtus I., possibly even earlier. The further developments do not concern us here.
Here and there in the West, there was a tendency to commemorate the death and resurrection of Christ on fixed days in the Julian Calendar—on the 25th and 27th of March, for example—but it never became general. For the most part, the data for the calculation of Easter were the same as those employed for calculating the Jewish passover; that is to say, the full moon on the one hand, and the vernal equinox on the other, Sunday being introduced as an additional factor in the calculation, since our Lord had risen on that day of the week. In this way the above rule was established, and so, in the date of Easter as determined at the present day, the variable Jewish lunar year has left a trace behind it, and, also, the connection in which Christianity stands to Judaism receives a practical expression deserving of being preserved to the end of time.[108]