In Aviv Barley and the Spirit of Constantine, Nehemia shows how the Council of Nicaea in 325 AD led to a change in the observance of the Biblical Calendar for both Jews and Christians. He also includes his educated guess as to when Passover will fall out this year based on the Aviv-New Moon calendar.
Learn more about Aviv Barley.
Mishawayh al Ukbari, 9th century Quasi Karaite
“All money is a convenience, so cleave to the counterfeit money in hand.”
Eusebius, Life of Constantine, Chapter 18
“For their boast is absurd indeed, that it is not in our power without instruction from them to observe these things. For how should they be capable of forming a sound judgment, who, since their parricidal guilt in slaying their Lord, have been subject to the direction, not of reason, but of ungoverned passion, and are swayed by every impulse of the mad spirit that is in them? Hence it is that on this point as well as others they have no perception of the truth, so that, being altogether ignorant of the true adjustment of this question, they sometimes celebrate Easter twice in the same year. Why then should we follow those who are confessedly in grievous error? Surely we shall never consent to keep this feast a second time in the same year.”
Mishnah, Rosh Hashanah 2:9
“[Rabbi Akiva] said to [Rabbi Joshua] ...whether they are proclaimed at their proper time or not at their proper time, I have no appointed seasons save these.” Rosh Hashanah 21b
Babylonian Talmud, Rosh Hashanah 25a
"[Rabbi Akiva] then said to [Rabbi Joshua]: The text says, ‘you’, ‘you’, ‘you’, three times, to indicate that ‘you’ [may set the festivals] even if you err inadvertently, ‘you’, even if you err deliberately, ‘you’, even if you are misled. He replied to him in these words: 'Akiba, you have comforted me, you have comforted me.'
Babylonian Talmud, Sanhedrin 11b
"Our Rabbis taught, Based on three things is the year intercalated: on the Abib, on the fruits of the trees, and on the equinox. Based on two of them the year is intercalated but based on one of them alone the year is not intercalated. And when the Abib is one of them everyone is pleased."
Babylonian Talmud, Sanhedrin 11b
"It once happened that Rabban Gamaliel was sitting on a step on the Temple Mount, and the well known Scribe Yohanan was standing before him with three cut sheets [of parchment] lying before him. He said to him, ...take the third [sheet] and write to our brethren, the Exiles of Babylon and to those in Media, and to all the other exiled [sons] of Israel, saying: 'May your peace be great forever! We beg to inform that the doves are still tender, and the lambs are still young, and time of the Aviv has not yet arrived (וזמנא דאביבא לא מטא). It seems advisable to me and to my colleagues to add thirty days to this year.'"
Babylonian Talmud, Sanhedrin 12a
"Our Rabbis taught: We may not in the current year, intercalate the following year, nor intercalate three years in succession. R. Simeon said: It once happened that R. Akiva, when kept in prison, intercalated three years in succession."
Babylonian Talmud, Sanhedrin 18b
“Were there not three cowboys who were standing conversing, and who were overheard by the Rabbis. One of them said: If the early and late sowing sprout together, the month is Adar; if not, it is not Adar. The second said: If in the morning frost is severe enough to injure an ox, and at mid-day the ox lies in the shade of the fig-tree and scratches its hide, then it is Adar, if not, it is not Adar. And the third said: When a strong east wind is blowing and your breath can prevail against it, the month is Adar; if not, it is not Adar. Thereupon the Rabbis intercalated the year. — Is it possible that the Rabbis really intercalated the year based on the determination of cowboys? Surely they relied on their own calculations, and the cowboys merely corroborated their proposed action.”
Babylonian Talmud, Sanhedrin 12a
"Was not a message sent to Rava: 'A couple [of scholars] have arrived from Rakkat [=Tiberias] who had been captured by an eagle while in the possession of articles manufactured at Luz [cf. Babylonian Talmud, Sota 46b]..., yet through divine mercy and their own merits they escaped safely. Further, the offspring of Nachshon wished to establish a Netziv [1Ki 4:19], but the Edomite there would not permit it..."
Judah Hadassi, Eshkol Hakofer, 12th Century
"but those distant from the testimony of the sighting of its ripening, from the Land of Israel, they are required to investigate and ask those that arrive from the Land of Israel, perhaps those in the Diaspora can receive from those that dwell in the Land of Israel proof of its testimony... therefore we who are in this exile, which has lasted for a long time because of our sins and the iniquities of our fathers, do not know which year is 12 months and which 13 except by seeking a testimony or report from the Holy Land"
Israel Hama'aravi, Seder Inyan Ha'ibur, 1313
"Most of the Karaite sages confess that it is good to follow the 19-year cycle because it is a close approximation of the Abib found in the Land of Israel. But the Karaite Israelites who live near the Land of Israel, specifically, the communities of Cairo and Alexandria, and the communities of Damascus and Aleppo. These communities send reliable emissaries each and every year to the Land of Israel who search out and investigate the barley in all the places where it is known from previous experience to ripen earliest. If they find a field that has ripened they take about two sheaves from the stalks of barley and bring them as testimony of the Abib. They show their communities the Abib and keep the Passover. The emissaries return to all these communities no later than the tenth of Nissan."
Rabbi Elijah of Salonika, 11th Century
"But you know, my dear brother, that the Karaites further provoked us last year and desecrated the holy holidays of the Lord and observed Rosh Hashanah in the Eighth Month because they received letters from the Land of Israel that the Abib was not seen in Nissan and Passover was kept in Iyyar..."
Samuel ben David of Crimea, 1641
"[p.226] ...and afterwards we traveled from there and arrived in Constantinople on the 25th of the month. We remained there 48 days... in the year 5402 [=1641]... and on the first holy day of the Feast of Sukkot we traveled from Constantinople... [p.231] ...and we awoke in the morning and went to Cairo on Friday, the 12th of the month... and dwelt there and kept the Feast of Sukkot a second time on the 15th of the month of Cheshvan, to keep the holy appointed times of the Lord according to the sighting of the new moon and the finding of the Abib in the holy land of Israel."