החדש הזה לכם - האמנם?

(1) The months of the year are lunar months, as it is stated (Numbers 28:14), "the monthly burnt-offering for each new moon"; and it is [also] stated (Exodus 12:2), "This month shall be for you the beginning of the months." Thus did the Sages say: The Holy One, blessed be He, showed Moshe a likeness of the moon in a prophetic vision and said to him, "See [when] it is like this, and sanctify it (as the beginning of the month)." But the years that we calculate are solar years, as it is stated (Deuteronomy 16:1), "Guard the month of the Spring."

(2) The solar year exceeds the lunar year by eleven days, approximately. Hence, whenever this excess accumulates to about thirty days, somewhat more or less, one month is added and the year is made up of thirteen months and is called leap year. The year cannot consist of twelve months plus several days, because it is written: "Months of the year" (Exodus 12:2), implying that the year should be reckoned by months and not by days.

(3) The moon is invisible for about two days each month, or somewhat more or less: about one day at the end of the old month before it is close to the sun and about one day after its conjunction with the sun, when it reappears in the evening in the west. The night on which it becomes visible in the west after having disappeared is the beginning of the month. Twenty-nine days are counted from that day on. If the new moon appears on the night of the thirtieth day, then the thirtieth day is the first day of the new month. If it does not appear on that night, the thirtieth day belongs to the past month and the thirty-first day is the first day of the new month. We pay no attention as to whether or not the moon appeared on the night of the thirty-first day, because the lunar month never exceeds thirty days.

(4) If the moon appears on the night of the thirtieth day, the past month has twenty-nine days and is called defective month. If the moon does not appear on the night of the thirtieth day, the past month has thirty days and is called intercalated month or full month. And a moon that is seen on the night of the thirtieth is what is called a moon that is seen in its time. And if it is seen on the night of the thirty-first and it is not seen on the night of the thirtieth, it is what is called a moon that is seen on the night of its intercalation.

(5) The observation of the new moon is not entrusted to every individual, as in the case of the regular weekly Sabbath where anyone may count six days and rest on the seventh, but the authority is given to the court only, to sanctify and proclaim the day as the first of the month. The day proclaimed by the court is Rosh Hodesh, as it is written: "This month shall be to you" (Exodus 12:2), implying that the evidence in this matter is surrendered to you [members of the court].

(6) Like astronomers who engage in calculation and know the positions and motions of the stars, the Jewish court calculates and investigates minutely so as to know if it is or is not possible for the new moon to be visible in its time, which is the night of the thirtieth day. If the members of the court found that it would be possible, they had to wait in the court house for the arrival of witnesses throughout the thirtieth day. If witnesses arrived and were duly examined and tested and found trustworthy, the thirtieth day was sanctified as the first day of the new month. If the new moon did not appear and no witnesses arrived, that day was counted as the thirtieth of the past month which became an intercalated month. If, however, the members of the court knew by calculation that the new moon could not possibly be seen, they were not required to sit and wait for the arrival of witnesses the thirtieth day. If witnesses did come to testify that they had seen the new moon, it was certain that they were false witnesses, or that a semblance of the new moon appeared to them through the clouds, and was not the real moon.

(7) It is a positive commandment from the Torah upon the court to calculate and know if the [new] moon was seen or was not seen; and they should question the witnesses [to ascertain this] until they sanctify the [new] month. And they must send and inform the rest of the people which day is Rosh Chodesh (the first day of month), so that they would know which days are the holidays – as it is stated (Leviticus 23:2), "which you shall proclaim as holy occasions"; and it [also] states (Exodus 13:10), "And you shall keep this statute at its appointed time."

(8) The new moon days and the leap years are computed and proclaimed only in Eretz Yisrael, as it is written: "Out of Zion shall go forth instruction, and the word of the Lord from Jerusalem" (Isaiah 2:3). If, however, a great scholar was ordained in Eretz Yisrael and then emigrated to another country without leaving in Eretz Yisrael anyone equal to him in learning, he is permitted to compute and proclaim the new moon days and leap years outside the Land of Israel. And if he knows that in the Land of Israel [another] man became great like him – and it is not necessary to say, greater than him – it is surely forbidden for him to set and intercalate the month outside the Land. And if he did transgress and set it and intercalate it, he did not do anything (it is not effective).

(3) In six months of the year the messengers go out from the court in Jerusalem to report throughout Eretz Yisrael and the Diaspora which day was established as the New Moon, the thirtieth or the thirty-first day since the previous New Moon. They go out in the month of Nisan, due to Passover, so that people will know on which day to celebrate it; in the month of Av, due to the fast of the Ninth of Av; in Elul, due to Rosh HaShana, which begins thirty days after the New Moon of Elul; in Tishrei, due to the need to establish the correct dates on which to celebrate the Festivals of Tishrei, i.e., Yom Kippur and Sukkot; in Kislev, due to Hanukkah; and in Adar, due to Purim. And when the Temple was standing, messengers would also go out in the month of Iyyar due to small Passover, i.e., second Pesaḥ, which occurs on the fourteenth of Iyyar. This holiday allowed those who were ritually impure or on a distant journey on the fourteenth of Nisan, and therefore incapable of bringing the Paschal lamb at that time, to bring their Paschal lamb a month later.

(4) Only for the sake of two months may witnesses who saw the new moon desecrate Shabbat, should that be necessary in order for them to offer testimony before the court: For the month of Nisan and for the month of Tishrei, for in these months messengers are sent out to Syria, and by them, i.e., these months, the dates of the major Festivals are set: Yom Kippur, Sukkot, Passover, and Shavuot. And when the Temple was standing, the witnesses desecrated Shabbat for the fixing of the New Moon of all the months, due to the imperative of fixing the proper offering of the New Moon at the correct time.

(6) There was once an incident where more than forty pairs of witnesses were passing through on their way to Jerusalem to testify about the new moon, and Rabbi Akiva detained them in Lod, telling them that there was no need for them to desecrate Shabbat for this purpose. Rabban Gamliel sent a message to him: If you detain the many people who wish to testify about the new moon, you will cause them to stumble in the future. They will say: Why should we go, seeing that our testimony is unnecessary? At some point they will be needed, and no witnesses will come to the court.

(1) All that we have said concerning the fixation of Rosh Hodesh on the basis of observing the new moon, and concerning intercalation of the year because of the season or because of some other necessity, is applicable only to the Sanhedrin in Eretz Yisrael or to the members of the court who were ordained in Eretz Yisrael, to whom the Sanhedrin gave permission to act. Moses and Aaron were told: "This month shall be to you the beginning of months" (Exodus 12:2), and the sages have derived from an oral tradition going back to our teacher Moses that the meaning of this verse is: This evidence shall rest with you and your successors. When, however, no Sanhedrin exists in Eretz Yisrael, the new-moon days and the leap years are determined only by such methods of calculation as we are employing today.

(2) And this matter is a law of Moses from Sinai: That at a time that there is a Sanhedrin, we set [the new month] by sighting; and when the Sanhedrin does not exist, we set [it] according to this calculation that we [use] to calculate today, and we are not concerned about the sighting. Rather, sometimes the day we set with this calculation will be the day of sighting; [and sometimes it will be] a day before it, or a day after it. And that it will be after the sighting by a day is a wonder (i.e. very rare), and [only] in lands that are to the west of the Land of Israel.

(3) When did all Israel begin to use this method of calculation? During the last generation of the talmudic sages, when Eretz Yisrael was in ruins and no established court had survived there. In the times of [the Tannaim] the sages of the Mishnah, and also in the period of the talmudic sages prior to Abbayyé and Rava, the people relied on the courts of Eretz Yisrael for setting the calendar.

(4) When the Sanhedrin still existed and the calendar was set by observation, the inhabitants of Eretz Yisrael, and the places that could be reached by the messengers of Tishri on time, observed each festival one day only; whereas those who lived in more distant places that could not be reached by the messengers of Tishri in time observed two days, because of doubt, since they failed to know which day had been proclaimed as Rosh Hodesh by the men of Eretz Yisrael.

(5) At the present time, when no Sanhedrin and court of Eretz Yisrael are in existence, we set the calendar by calculation. It might be logical that the Jewish people everywhere, even those living in remote places of the Diaspora, should observe one day only [as holyday] just as the inhabitants of Eretz Yisrael do, in view of the same calculation followed by all in determining the calendar. The sages, however, have made it a rule that the people must carefully follow the custom of their forefathers.

(6) Accordingly, the localities which could not be reached on time by the messengers sent to announce Rosh Hodesh Tishri must observe two days even at present, just as they used to when the men of Eretz Yisrael determined the calendar on the basis of observation. But the residents of Eretz Yisrael at our time should continue to keep only one day, according to their [ancient] custom, for they never observed two days. Hence, it becomes evident that the second day of the festival that we observe in the Diaspora nowadays is something enacted by the sages.

(7) When the fixing of the month was accomplished by the observation method, the majority of the inhabitants of Eretz Yisrael observed Rosh Hashanah for two days, because they were in doubt as to which day had been declared as new-moon day, since the messengers could not go forth on a holyday [and Rosh Hashanah coincides with the first day of the month].

(8) Moreover, even in Jerusalem itself, which was the seat of the court, it frequently happened that Rosh Hashanah was observed for two days. If witnesses failed to arrive on the thirtieth day of Elul, the people were accustomed to celebrate it as Rosh Hashanah, while waiting for witnesses to appear, observing the following day likewise as a holyday. Since they used to keep two days Rosh Hashanah even when the method of observation was in use, the sages ordained that even the citizens of Eretz Yisrael should keep it for two days always, at the present time when the calendar is determined by computation. You may thus infer that even the second day of Rosh Hashanah is based on the authority of the sages.

(9) The observance of one day of the other festivals does not depend upon the proximity of a location to Jerusalem. For example, a locality at a distance of five days' journey or less from Jerusalem could certainly have been reached by the messengers in time; yet it cannot be said that the residents of this place should observe only one day. As who will tell us that the messengers went out to this place? possibly no messengers were ever sent out to this place because there were no Jews there, and when the calendar began to be determined by computation the place was settled by Jews who were required to observe two days by their previous custom. Or else, no messengers ever came to this place because of insecurity in travel, as was the case between Judea and Galilee during the period of [the Tannaim] the sages of the Mishnah, or, because non-Jews, living along the road, would prevent the messengers from passing through the area.

(10) If this matter of observing one day were to depend upon the proximity to Jerusalem, all the Jews of Egypt would observe only one day, since the messengers of Tishri could have reached them in time. The distance between Jerusalem and Egypt, by way of Ashkelon, is indeed only a matter of eight days' journey or less. The same applies to most places in Syria. Hence you may infer that the thing does not depend upon the proximity of a place.

(11) It is found that the principle of this matter in this way is such: Any place that has a journey more than ten complete days between it and Jerusalem always makes two days, like their custom from before. For the messengers of each and every Tishrei would only reach a place that has a journey of ten days or less between it and Jerusalem. And any place that has a journey exactly ten days or less between it and Jerusalem – such that it is possible that the messengers of Tishrei would reach it – we see if that place was from [a part of] the land of Israel that had Israelites in it at the time of the sighting in the second conquest [of the Land]. For example, Usha and Shaphram and Lod and Yavneh and Nov and Tiberius and that which is similar to them. [In that case,] they make only one day alone. But if the place was of Syria – such as Tyre and Damascus, and Ashkelon and that which is similar to them; or from outside of the Land [of Israel] – like Egypt and Ammon and Moab and that which is similar to them – they do like the custom of their fathers which is in their hands: If one day, one day; and if two days, two days.

(12) [In the case of] a place that has ten days or less than ten between it and Jerusalem, and it is [in] Syria or outside of the Land, and they don't have a custom; or it is a newly formed city in the wilderness of the Land of Israel; or a place that Israelites inhabited now: They make two days like the custom of the majority of the world. And every second day holiday is from the words of the Scribes (rabbinic); and even the second day of the holiday of Rosh Hashanah which everyone makes at this time.

(13) When we nowadays compute, everyone in his own town, declaring such and such a date to be Rosh Hodesh or a festival, we do not rely upon our own calculation and determination, for it is not permissible to intercalate the years or to determine new-moon days outside of Eretz Yisrael; we may rely only on the computation and fixation performed by the inhabitants of Eretz Yisrael. Our own computation is only for the purpose of making it known to the public; since we are aware that in Eretz Yisrael they use the same method of computation, we calculate in order to find out what day it is that has been determined by the residents of Eretz Yisrael. And it is [the date] that the residents of the Land of Israel set, that will be Rosh Chodesh or the holiday. [It is] not on account of the calculation that we calculate.