Skip to main content

7th Day Sabbath Churches of God

Beliefs & Modern History
Churches - United States
Churches - International
Church of God News
Live Services/Bible Studies
Biblical Calendar 2015
Passover / F.U.B. 2015
Pentecost Weekend 2015
Tabernacles 2015: USA
Tabernacles 2015: Internat'l
Free Literature & DVDs
Bible Studies
God's 7000 Year Plan/Jubilee
Matthew 28:19 & Trinity
Contact Us

Translate this page

Biblical Calendar 2015

The ‘Biblical’ Calendar is even more complicated than usual in 2015 ...

One church is even Changing the Rules of its Biblical Calendar for 2015

- resulting in the dates being brought forward by a month!

(See letter below calendar dates.)

A History of the Biblical Calendar’ is a work in progress

and is continued below the letter ...

(but we'll check the apostrophe's)

The seven ‘Biblical’ calendars observed by the 7th Day Churches of God (within which there are variations), including the 2015 dates, are shown below.

[0] Hebrew (i.e. Jewish) Calendar - a link is given here, as a few groups keep Passover and/or Pentecost on the Jewish calendar dates, and also non-Biblical Jewish festivals.

[1] Churches of God Hebrew Calendar

The largest Church of God 7th Day (HQ in Denver) and the largest offshoots of the Worldwide Church of God utilize the mathematical framework of the Hebrew calendar, but observe some of God's appointed times on different dates.

As 12 lunar months equal 354 days, a lunar calendar has to add (intercalate’) a 13th month every 2 or 3 years to keep it in line with the solar year. The Hebrew calendar does this in years 3, 6, 8, 11, 14, 17 & 19 of a 19 year cycle.

The Hebrew calendar year begins at the Molad Emtzai, which in 2015 will be on Sunday, 13th September. The postponement rules do not, however, allow the year to begin on a Sunday, so the Day of Trumpets will be on Monday, 14th September.

First day of the dark phase of the moon, nearest the March Equinox.
[00.45, 21st March, Jerusalem time], when the light of the old moon has disappeared.]

(Only two small churches are known to use this calendar system, and none are known to use the first day of the dark phase of the moon, following the March equinox.)

[3] Day of the astronomical new moon (conjunction of sun/moon) [11.36, 20th March], nearest the March Equinox [00.45, 21st March, Jerusalem time].

[4] Day of the astronomical new moon (conjunction of sun/moon), [20.57, 18th April],

following the March equinox [00.45, 21st March, Jerusalem time].

For some groups it's the day after the conjunction – i.e. the same day as the Equinox -

assuming Jerusalem time is being utilized.

[5] Evening of the re-appearance of the light of the moon – visible in the brief period between sunset and moonset - nearest the March equinox.

[6] Evening of the re-appearance of the light of the moon – visible in the brief period between sunset and moonset - following the March equinox..

[7] Evening of the re-appearance of the light of the moon – visible in the brief period between sunset and moonset- in the month that the wild barley in Israel will be ready for harvesting by the Sunday after Passover (Leviticus 23:10-12).

The dates below are based on New Moon and Equinox times at Jerusalem, but if other time zones are used, the dates might be a month different.

The dates for the 3 annual festivals (Exodus 23:14-16)
are printed in green, and the 7 annual holy days are in red.


21 Mar
20 Mar
20 Mar

19 Apr
22 Mar


3 April
2 April
2 April

2 May

4 April

Festival of




First Day of
4 April
3 April
3 April
3 May

5 April

Seventh Day
of Unleavened
10 April
9 April
9 April

9 May

11 April

Festival of

24 May
24 May
24 May
21 June

24 May
Day of

14 Sept
12 Sept

13 Sept

13 Oct

** Tues
15 Sept
Day of
23 Sept
21 Sept
22 Sept

22 Oct

24 Sept
Festival of
28 Sept
- 4 Oct
26 Sept
- 2 Oct
27 Sept
- 3 Oct

27 Oct
- 3 Nov

29 Sept
- 5 Oct

First Day of

28 Sept
26 Sept
27 Sept

27 Oct

29 Sept

Eighth Day
5 Oct

3 Oct

4 Oct

3 Nov

6 Oct

*The new moon was certain to have been visible on the evening of 21 March,
but the sky was cloudy over Jerusalem. For those who require sighting by the
naked eye at Jerusalem, these dates are a day later - and Pentecost is 31 May.
New moon first visible possibly the following day

Changing the Rules of the Biblical Calendar for 2015

Don Esposito of the Congregation of Yahweh (Jerusalem) has written to his members to explain why he is beginning the biblical year on March 21, which is contrary to the calendar rules in Lesson 11 of his correspondence course, ‘The Biblical Calendar’ :

“Clearly from scripture we are to start the year in spring after the vernal equinox and not in winter before it; thus, the next new moon after the equinox was the beginning month of Aviv, thus always occurring in the spring.” (p.7)

In 2015 the March equinox will occur at 00.45 on March 21 (Jerusalem time).

By ‘new moon’, he means the astronomical new moon (conjunction of sun and moon), which will occur at 11.36 on March 20 and 20.57 on April 18 (Jerusalem times). He begins a month at the following sunset, so the new year should begin at sunset on April 19. However, he will begin the new year at sunset (17.51) on March 21, almost 5 hours before the equinox.

His letter, ‘2015 and the Start of the Year’, shows that he is adjusting his ‘biblical calendar’ - method [4] - in order to bring forward the start of the year by one month, because his ‘biblical calendar’ does not synchronize with the Aviv barley method [7]

“Since the conjunction actually happens a few hours before the equinox (it actually happens 13 hours before, on the 20th), some may wrongly assume that there should be another month added to the calendar, which would be inaccurate, since March 21, 2015 is both the first day of spring and also the first day of the new month, which would have to be Aviv, since spring and the new year would already be here.

The day of the equinox is NOT the last day of the old year but the first day of Spring/Summer, one can verify this on any celestial website including The day starts at the following sunset after conjunction, which in this case is the same day as the equinox, which makes it Aviv one. The month is based on the day cycle, but the year is based on the season and moon cycle.

The biblical calendar is a cyclical calendar based on both the celestial movement of the sun, moon and stars and confirmed by the agriculture in Israel. In 2015 the cycle is complete and the equinox occurs on March 21, which is also the first day of the new month, which would make it Aviv one, and not Adar 2. To wait a full extra month would make no sense and would throw off the entire agricultural cycle in which I have witnessed to for the last 15 years here in Israel.” ....

“One thing that has been amazing is in my 15 years living here in Israel not once has the agricultural cycle ever disagreed with the biblical calendar, but each year confirmed it. This can only come from Yahweh, as some years start early as this year and some years later, but every year was confirmed by Yahweh from heaven from the harvest fruits at the proper time.

This year we got such early rain in November as never before and everything turned green one month early in mid November instead of mid December. I have never seen it happen this early in the 15 years I have been here and the almost 20 years of coming to Israel. So I can almost say with certainty that there will be Aviv barley in March in preparation for the feast of firstfruits as the barley grass is already about 3 inches high, which is extremely rare for this time of year. The miracle is it could have just as easily gone the other way like last year, which had very little rain and later barley, but again Yahweh confirms His biblical calendar from His Holy Land.

I apologize if our literature on this subject made it somewhat confusing, since we stated that to start the year you should wait until after the equinox and then the next new moon is Aviv one, but it is more properly stated you should wait ‘until the equinox and then start the new year as in cases such as 2015, where the equinox (new year) and new moon (new month) fall on the same day, making it clearly Aviv 1, and not Adar 2. Neither word is in scripture but is assumed and. when taking the whole calendar into account, including the agricultural cycle here in Israel, than it is clear that ‘until’ is more properly implied than ‘after’.”

A History of the Biblical Calendar

Scriptural References :

ASV - American Standard Version; GLV - Green's Literal Version

The sun and moon declare our annual appointed times with God:

And God said, Let there be lights in the firmament of heaven to divide the day from the night; and let them be for signs, and for seasons, and for days and years ... And God made the two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also.(Genesis 1:14,16 ASV)

These are appointed seasons of Jehovah, holy gatherings which you shall proclaim in their appointed seasons (Leviticus 23:4 GLV)

Chodesh (Strong’s H2320) is defined as ‘the new moon; by implication, a month’.

This month
(chodesh) shall be unto you the beginning of months: it shall be the first month of the year to you. (Exodus 12:2 ASV)

Observe the month 
(chodesh) of Abib, and keep the passover unto Jehovah thy God; for in the month of Abib Jehovah thy God brought thee forth out of Egypt by night.
(Deuteronomy 16:1 ASV)

Each Biblical month begins at the new moon, and the first month of the year is Abib (Nisan), the month of the Passover.
(The Egyptian calendar began with the season of Inundation [of the Nile] in midsummer, which was prefaced by the appearance of Sirius just before dawn. Each day began at sunrise, while the month began at the sunrise following the disappearance of the old moon.)

Originally every month was 30 days long – as shown by Noah’s flood, when “the waters prevailed over the earth one hundred and fifty days” (Genesis 7:24), from the seventeenth day of the second month” (7:11) to the seventeenth day of the seventh month” (8:4) – 5 months of 30 days each. Today, a lunar month is either 29 or 30 days, and it is impossible for there to be 5 consecutive months of 30 days each.

Exodus 12:2 and Deuteronomy 16:1 were therefore all the calendar instruction that the Israelites needed – there was no requirement to add a 13th lunar month every 2 or 3 years to align the calendar with the solar year.

Ancient documents confirm that a year comprised 12 months of 30 days each:

“At first the astronomers of Babylon recognized a year of 360 days, and the division of a circle into 360 degrees must have indicated the path traversed by the sun each day in its assumed circling of the earth.” (
Moritz Cantor, Lectures on the History of Mathematics.)

“The Assyrians, like the Babylonians, had a year composed of lunar months .... The calendar assigns to each month thirty full days.” (
R. Campbell Thompson, Reports of the Magicians and Astrologers of Nineveh and Babylon in the British Museum.)

“A year consists of twelve months. A month consists of 30 days.” (The Arabhatiya of Aryabhata – an ancient Indian work on mathematics and astronomy)

“All over the world we find that there was at some time the same calendar of 360 days, and that at some later date, about the seventh century before the present era, five days were added at the end of the year, as ‘days over the year’, or ‘days of nothing’ ... a series of catastrophes occurred that changed the axis and the orbit of the earth and the orbit of the moon ...” (
Immanuel Velikovsky, Worlds in Collision)

“Yet the fact is that no one has ever established that the 365-day calendar was in use prior to the early seventh century.” (
Mark Cohen, The Cultic Calendars of the Ancient Near East.)

This was the time period of the Old Testament prophets and of Daniel, when:
“He is changing times and seasons” (Daniel 2:21 - Young's Literal Translation)

What was affecting the Earth and causing the “changing times and seasons”?

At the Babylonian Akitu festival, the high priest would recite
the following prayer before the statue of Bel - a.k.a. Marduk:
(“Babylon is captured, Bel is put to shame, Merodach is broken in pieces, her images are put to shame, her idols are broken in pieces.”
- Jeremiah 50:2 GLV):
“My lord is just. Is his name not ‘My-Lord’?
My lord causes trembling. My lord is the prince of all the lands ...
Jupiter, bearer of signs to the universe! My Lord! My Lord, be calmed!
Mercury, who brings rain! My Lord! My Lord, be calmed!
Saturn, star of justice and right! My Lord! My Lord, be calmed!
Mars, blazing fire! My Lord! My Lord, be calmed! ...”

The high priest then turned to pray to Bel’s consort, Beltiya:
“My lady, turn back! Turn back! My lady, be calmed! ...
Venus, brightest star - this is a name for my lady,
Bow-star, who fells the mighty - this is a name for my lady,
She-goat star, who scans the heavens - this is a name for my lady,
Star of Abundance, the star of abundance - this is a name for my lady,
Star of Dignity, the star which moves out of orbit ...”
Mark Cohen, The Cultic Calendars Of The Ancient Near East)

“Bel, thine abode is Babylon ... thou controllest laws by thy laws ... thou burnest up the mighty ones by thy flame.” (
Stephen H. Langdon, The Mythology of All Races)

“By causing the heavens to tremble and the earth to quake,
By the gleam which lightens the sky,
By the blazing fire which rains upon the hostile land,
I am Ishtar. Ishtar I am by the light that arises in heaven,
Ishtar the queen of heaven am I by the light that arises in heaven.”
Stephen H. Langdon, Sumerian and Babylonian Psalms)

How did the nations adjust to a solar year of 365 days and months of 29 or 30 days? Most retained twelve 30 day months and added ‘5 days of nothing’ at the end of the year. For example, “The Peruvian year was divided into twelve Quilla, or moons, of 30 days. Five days were added at the end, called Allcacanquis.”

(Sir Clements Markham, The Incas of Peru)

In 238BC a decree at Canopus, Egypt, declared, “from this time onwards one day, a festival of the Good-doing Gods, shall be added every four years to the five additional days before the New Year, so that all may know that the error of deficiency which existed formerly in respect to the arrangement of the seasons, and of the year, and of the views usually believed concerning the general ordering of the heavens, hath been rectified and filled up satisfactorily by the Good-doing Gods.”

Daniel and his companions were taken captive to Babylon during this period when Jehovah “is changing the times and the seasons”. Nebuchadnezzar found these young men to be “skilful in all wisdom, and endued with knowledge, and understanding science” (Daniel 1:4 ASV). “And in every matter of wisdom and understanding, concerning which the king inquired of them, he found them ten times better than all the magicians and enchanters that were in all his realm.” (Daniel 1:19-20 ASV).

Was it due to their influence that the Babylonians retained a luni-solar calendar?”

The months were strictly lunar (in this case, because it was the first visibility of the new crescent that marked the start off each new month), and those lunar months were combined with a variable year that could average out to the same length as the solar year. Every two or three years an intercalary lunar month was added (usually a second Ulul [6th month] or a second Adar [12th month]).
(Mark Cohen, The Cultic Calendars of the Ancient Near East)

On the basis of three letters which record the announcement of the intercalary year, Parker and Dubberstein [authors of Babylonian Chronology: 626BC-AD75] suggest that, during the Babylonian period, the directives for intercalation came from the king, whereas during the subsequent Achaemenid period [Persian empire], priestly officials in Babylon gave the orders.” (ibid)

The intercalation of a 13th month is evident in the book of Ezekiel, written during the Babylonian captivity:
“.... in the fourth month, on the fifth day of the month .... In the fifth day of the month, which was the fifth year of king Jehoiachin's captivity, the word of Jehovah came expressly unto Ezekiel ....(1:1-3 ASV). After Ezekiel had dwelt at Tel Aviv for 7 days (3:15), the word of Jehovah came again, saying that he should lie on his left side for 390 days, then on his right side for 40 days (4:4-6). More than 437 days had thus elapsed when Ezekiel was sitting in his house on the 5th day of the 6th month in the 6th year, i.e. 1 year 2 months later (8:1).

14 months x 30 days + 5 days = 425 days. Since the lunar month now averaged 29½ days, a 13th month must have been intercalated during this period.

14 months x 29½ days = 413 days + intercalary month = 442 or 443 days.

After 70 years captivity in Babylon: “in the first year of Cyrus king of Persia, that the word of Jehovah by the mouth of Jeremiah (Jer.29:10) might be accomplished, Jehovah stirred up the spirit of Cyrus king of Persia, so that he made a proclamation throughout all his kingdom, and put it also in writing, saying ... ‘Whosoever there is among you of all his people, his God be with him, and let him go up to Jerusalem, which is in Judah, and build the house of Jehovah, the God of Israel (he is God), which is in Jerusalem ...When rose up the heads of fathers' houses of Judah and Benjamin, and the priests, and the Levites, even all whose spirit God had stirred to go up to build the house of Jehovah which is in Jerusalem’.” (Ezra 1:1,3,5 ASV)

And when the seventh month was come, and the children of Israel were in the cities, the people gathered themselves together as one man to Jerusalem ...And they kept the feast of tabernacles, as it is written.
(Ezra 3:1,4 ASV)

And Ezra the priest brought the law before the assembly, both men and women, and all that could hear with understanding, upon the first day of the seventh month ...And they found written in the law, how that Jehovah had commanded by Moses, that the children of Israel should dwell in booths in the feast of the seventh month ... Also day by day, from the first day unto the last day, he read in the book of the law of God. And they kept the feast seven days; and on the eighth day was a solemn assembly, according unto the ordinance. (Nehemiah 8:2,14,18 ASV)

How did Ezra determine when it was the 7th biblical month? What instruction did he receive from Daniel - who was alive during the reign of Cyrus (Dan.6:28)? The books of Ezra and Nehemiah contain no definite statements as to the calendar rules, but detailed information of the Second Temple calendar can be found in the Mishnah, a collection of 63 tractates, divided into 6 orders, one being the Mo’edim (the appointed times of Jehovah).

“The calendar of the Mishnah is discussed and debated in detail in both the Palestinian and the Babylonian Talmudim … The fact that no other calendar system is ever referred to in the Talmudim may be regarded as significant. In the absence of evidence to the contrary, it is reasonable to assume that the Mishnaic system was perpetuated well into the Amoraic period (third to fifth centuries).”

(Sacha Stern, Calendar and Community : A History of the Jewish Calendar, 2nd century BCE – 10th century CE, p.164)

There were other calendars in Palestine during this period in history, most notably the Samaritan calendar of the Northern Israelites, who continue to this day to observe the annual festivals at Mount Gerizim. Jesus Christ, however, observed the annual festivals in Jerusalem, so the focus must be on the calendar there.

The procedure for determining the beginning of a month is described at length in tractate Rosh ha-Shanah, and is graphically described on the Temple Institute website.

The gospels show that Jesus Christ died in the late afternoon of the 14th of Abib, the preparation day for the High Day, the 15th of Abib, on the Jewish Temple calendar.

‘The Jews therefore, because it was the Preparation, that the bodies should not remain on the cross upon the sabbath (for the day of that sabbath was a high day), asked of Pilate that their legs might be broken, and that they might be taken away.’ (John 19:31 ASV)

The procedure for determining the beginning of a year is described in detail in the Tosefta, Tractate Sanhedrin, section 5:2. Herbert Danby, in the introduction to his translation of Tractate Sanhedrin, issues a warning about the Tosefta: “The Mishnah and Tosefta, which are here translated, may be regarded as together giving the bulk of the traditions on the subject in the form in which they existed at the close of the second century A.D. The Mishnah gives an ordered, comprehensive sketch of the regulations which governed the legal courts; while the Tosefta goes over similar ground in a freer manner, frequently repeating, occasionally contradicting, and constantly supplementing not always relevantly the substance of the more authoritative and final code.”

Much of Tractate Sanhedrin 5:2 is rabbinic opinion, which must be stripped away, and the basic reasons given for intercalation compared with Scripture.

5.2.2. There are three signs which make it evident that the year should be intercalated:

(a) the premature state of the corn-crops

“Speak unto the children of Israel, and say unto them, When ye are come into the land which I give unto you, and shall reap the harvest thereof, then ye shall bring the sheaf of the first-fruits of your harvest unto the priest: and he shall wave the sheaf before Jehovah, to be accepted for you: on the morrow after the sabbath the priest shall wave it.” (Leviticus 23:10-11 ASV)

“Seven weeks shalt thou number unto thee: from the time thou beginnest to put the sickle to the standing grain shalt thou begin to number seven weeks ... And thou shalt keep the feast of weeks unto Jehovah thy God ...” (Deuteronomy 16:9-10 ASV)

If the fields of barley (which grows wild all over Palestine) are not ready to begin harvesting on the Sunday after Passover, a 13th month was to be added.

(b) The undeveloped state of the tree products

And He spoke a parable to them: ‘You see the fig tree and all the trees ... Now when they sprout leaves, seeing it, you will know from yourselves that now the summer is near.’ (Luke 21:29-30 GLV)

For, lo, the winter is past; The rain is over and gone; The flowers appear on the earth; The time of the singing of birds is come, And the voice of the turtle-dove is heard in our land; The fig-tree ripeneth her green figs, And the vines are in blossom; They give forth their fragrance. (Song of Solomon 2:11-13 ASV)

Here are given two other indicators of the end of winter and the beginning of summer: the end of the rainy winter season and bird migration.

(c) The lateness of the spring equinox

Summer and Winter are the only biblical seasons. The season of Spring cannot be found in the scriptures.

Equinox here derives from the Hebrew word tqufah (Strong’s H8622), which is found in 4 verses:
And you shall observe a Feast of Weeks for yourself, the firstfruits of the harvest of wheat; also the Feast of Ingathering at the turn of the year.(Exodus 34:22 GLV)

And it happened when the time had come around, Hannah conceived and bore a son.(1 Samuel 1:20 GLV)

And it happened, at the turn of the year, that the army of Syria came up against him ...
(2 Chronicles 24:23 GLV)

his going forth from the end of the heavens, and his orbit to their ends
(Psalm 19:6 GLV)

The ‘spring equinox’ is the result of rabbinic teaching that the ‘turn of the year’ in Exodus 34:22 may be interpreted as ‘equinox’ - thus fixing the time of the Festival of Tabernacles at the September equinox - then they taught that the March equinox was also a tqufah - and subsequently that the two solstices were also tqufahs - thus four seasons.

The vernal equinox occurs on March 20 or 21 every year. It cannot therefore be either late or early.

Tshubah (Strong’s H8666) is the ‘end of the year’ - the end of winter - in 2 Samuel 11:1; 1 Kings 20:22,26; 1 Chronicles 20:1; 2 Chronicles 36:10.

(It is used in a different sense in 1 Samuel 7:17, Job 21:34 and Job 34:36).

The kings usually waited until the end of winter to begin their military campaigns, because the rains had ceased (Song of Solomon 2:11), facilitating easier troop movement.

The ‘lateness of the tqufah’ (or tshubah) meant that the weather had not yet turned – it was still wintry.

5.2.3 On the basis of evidence derived from three countries used they to intercalate the year: Judaea, the land beyond Jordan, and Galilee. They may intercalate on the basis of two of these, but not of one only; though in this latter case the intercalation would hold good. And if Judaea were one of the two they rejoiced, because it was from there that the offering of the firstfruits came.

The ripeness of the barley was assessed in the above three areas.

5.2.4, 5.2.5 & 5.2.6 The following were additional indicators in years when there was doubt about the barley being ready for harvesting.

5.2.4 The season of the kids or lambs or pigeons had not yet arrived.

5.2.5. R. Jannai said in the name of Rabban Shimeon, the son of Gamaliel: He used to say: “In that the pigeons are still tender (Song of Solomon 2:12) and the spring Iambs thin (Exodus 12:2,3,5), it is fitting in my opinion to add thirty days to this year.”

5.2.6 Repetition of 5.2.5 with more detail.

“This month shall be unto you the beginning of months: it shall be the first month of the year to you ... In the tenth day of this month they shall take to them every man a lamb.” (Exodus 12:2,3 ASV)

5.2.7 The year is not to be intercalated unless the spring equinox is still distant the greater part of a month.

The Mishnah records that the new year declaration (Rosh ha-Shanah) was publicized throughout the land and further north into the diaspora by a system of beacons (but later via messengers. The Palestinian and Babylonian Talmudim both write of another chain of beacons eastward across Jordan to Pumbeditha in Babylonia.

Rabbi Gamliel is recorded as sending letters to the brethren in Syria, Asia Minor (Turkey), Media (western Iran) and Yawan (Macedonia).

The new moon was declared in the morning, so it was impossible for those in the diaspora to receive the news by the end of that day. The distance from Jerusalem to Babylon by road is 900 miles. Even if they’d had the resources of the Pony Express, whose team of riders could cover up to 250 miles in 24 hours, it would have taken 4 days to reach Babylon. The reality seems to have been much slower and less reliable.

Rather than use local new moon sighting, Jews in the diaspora bowed to the authority of the Palestinian calendar court, and observed each annual holy day for 2 days, in order to be sure of keeping the day that the court had sanctified. This tradition continues today for Orthodox Jews living outside Israel (except for the Day of Atonement - to avoid fasting for two successive days).

A ‘rule of the equinox’ was agreed for use when news regarding intercalation had not been received from Palestine by Passover - and if this proved to be the wrong decision, correction was made for subsequent appointed times.

“The rule of the equinox is attested in a single passage in the Babylonian Talmud (Rosh ha-Shanah 21a) ... implies that 15 Nisan, the first day of Unleavened bread, cannot occur before the vernal equinox. In this recension, the term aviv is treated as synonymous with tequfah (equinox).” (Sacha Stern, ibid, p.167)

The computation of the equinox - Tequfah Nisan - was based on a solar year of 365¼ days, which is inaccurate for long term use, but it remains part of the modern calculated calendar for ritual purposes. (Tequfah Nisan is now 7-8 April - 18 days later than the true equinox.)

“With the introduction of the permanent calendar ... the independent computation of the beginnings of the four seasons, the Tequfoth, has lost its importance. Nevertheless, in all our annual calendars we find the dates of the four Tqufoth listed ... on the day of Tequfah Nisan in the first year of the 28-year sun cycle ... we praise God as the Creator of the universe and especially of the sun in a special blessing.”

(Arthur Spier, The Comprehensive Hebrew Calendar)

Jewish communities outside the land and Christian churches, most of whom had no desire to follow ‘the practice of the Jews’, followed various time cycles, usually based around the equinox, for calculating future dates for Passover/Easter.

“We do not know how early the Easter cycles were used in practice by Christian communities, but by the early 4th century, and certainly by the Council of Nicea (325CE), the Roman cycle of 8 or 84 years had become standard in the West, and the Alexandrian cycle of 19 years in the East.” (Sacha Stern, ibid, p.225)

Emperor Constantine wrote to the Syrian and Palestinian absentees from the Council of Nicea: “It was resolved by the united judgement of all present that this feast ought to be kept by all and in every place on one and the same day ... And first of all it appeared an unworthy thing that, in the celebration of this most holy feast, we should follow the practice of the Jews.”

There was no unanimity at this council, however, as to the format for calculating Easter Sunday. In 525AD Dyonysius Exiguus published his Easter table, which the Roman Catholic church soon began to use. His paschal table is an adaptation of the 19 year Alexandrian cycle, with intercalations in years 3, 6, 8, 11, 14, 17 & 19. This table has the same cycle and leap year sequence that would later be adopted for the Jewish calculated calendar.

In the 7th century the Islamic Empire came to power in the Middle-east. The  Caliphate, which by the 9th century stretched from the Indian border to Spain, gave the Pharisees religious autonomy across the empire under a system known as the Exilarchate. Karaites and other Jewish groups vigorously opposed their religious governance, but could not prevent the Pharisees from becoming by far the dominant sect in Judaism (now known as ‘Orthodox’ Jews).
The raised status of the Pharisees is exemplified by the Exilarch of Babylon’s letter in 835/36, in which he referred to himself as “the head of the yeshivot, the rabbis and all Israel.” The exilarch supported the Palestinian court’s decision, however, since “we always rely on them, lest Israel be split into factions.”

“According to the exilarch, the setting of Passover on Tuesday was dictated by a concern to avoid visibility of the new moon before the first day of the month. This concern does not exist in the present-day rabbinic calendar.

Once discovered and published in 1922, the exilarch’s letter proved beyond doubt that, almost five hundred years after R. Yose and ‘Hillel the Patriarch’, the fixed calendar in its present-day form had still not been instituted.” (Sacha Stern, ibid, pp.184-5)

This deference to the Palestinian court’s decisions would not last much longer - and neither indeed would empirical observation.

Adapting the 19 year cycle to the calendrical rules that had gradually been developed over the previous centuries was a difficult task, and its achievement is generally credited to Rabbi Nahshon, Gaon of Sura in Southern Babylonia, 871-879AD. His ‘four parts’ or ‘four gates’ table (probably referring to the four days of the week on which 1st Tishri may fall - Monday, Tuesday, Thursday, Saturday) corresponds to the modern calendar - but requires the calculation of the ‘molad’.

“The earliest datable reference to the present day molad calculation is in the work of the Muslim astronomer al-Khwarizmi on the Jewish calendar, dating from 823/4CE, where the lunation of 29 days, 12 hours and 793 parts [1 hour = 1080 parts] is explicitly given.” (Sacha Stern, ibid, p.205)

“In the early 12th century Rabbi Avraham b. Hiyya acknowledged that the rabbinic mean lunation of 29 days, 12 hours and 793 parts, was identical with Ptolemy’s in his 2nd century classic work of astronomy, the Almagest ... It also appears indeed that the epoch assumed in the rabbinic calculation of the molad was based on that of Ptolemy.(Sacha Stern, ibid, p.207)

An alternative theory has been proposed - that ancient Babylonian astronomers had calculated this lunation, and that the Jews borrowed from them and not from Ptolemy.

“Whether the molad calculation was borrowed from Babylonian astronomers, or from an Arabic translation of Ptolemy’s Almagest that would have been made at the 9th century Abbasid capital of Baghad, in the heartland of Babylonia, the geographical origins of this molad would have been the same. It was in Babylonia, indeed, that this molad would have become known to the Jews and incorporated into the present-day rabbinic calendar.” (Sacha Stern, ibid, pp.209-10)

“Inasmuch as the present-day molad calculation and the ‘four parts table’ were both Babylonian in origin, the contribution of the Babylonian rabbinic community to the normative Jewish calendar would thus have been considerable: for the molad calculation and the ‘four parts table’ constitute the foundation of the present-day rabbinic calendar. There is thus a case to argue that the calendar in use nowadays is essentially a Babylonian calendar.” (Sacha Stern, ibid, p.275)

In the summer of 921AD a dispute arose between Palestine and Babylon, which was centered around the definition of the recently introduced rule of Molad Zaqen - ‘late conjunction’. (Fixed calendars were based on the ‘mean conjunction’ - the time of first visibility of the moon could not be calculated.)

The rule in the modern Jewish calendar states that, if the molad of Tishri occurs on or after the 18th hour (i.e. noon), the 1st of Tishri must be postponed to the next day.

This rule could not have been in effect in 835/6AD:-

“That molad zaqen was not observed is confirmed beyond doubt in the exilarch’s letter of 835/6CE, in which time the molad Nisan (836CE) is explicitly given as Tuesday ‘in the daytime ... at four hours’, i.e. approximately 10am ... This means therefore that the subsequent molad of Tishre, according to the exilarch’s reckoning, would have been on a Thursday at least 4 hours later, thus well into the afternoon. But since Passover of 836CE was to occur on a Tuesday (according to this same letter), the subsequent Rosh ha-Shanah would have been on a Thursday - on the day of the conjunction, when this conjunction occurred in the afternoon. This demonstrates that, as late as 835/6CE, the rule of molad zaqen was not yet observed.” (Sacha Stern, ibid, p.196)

This dispute arose from the announcement by the Palestinian Gaon in the summer of 921AD of the calendar dates for the next three years. Passover in 922AD was to be on Sunday, and the year ‘defective’ (one day less than the ‘regular’ year), whereas the Babylonian leadership had calculated that it would be on Tuesday, and the year ‘full’ (one day extra).

The Babylonians had calculated the molad of Tishri to be at 18 hours and 247 parts, thus the Molad Zaqen rule would come into effect. Ben Meir of Palestine argued that their ‘four gates table’ was in error by 642 parts (35 minutes 40 seconds). He issued an adjusted table, bringing the molad back by 642 parts - before noon - so that the rule did not apply. R. Saadia ben Yosef of Babylon complained that he had artificially superimposed his 642 parts on their table, and could give no explanation for this difference of 642 parts, other than saying it resulted from the ancient system of calculation handed down to him.

Ben Meir then proposed amending the Molad Zaqen rule to 18 hours 642 parts, which would affect the calendar far less. Changing the ‘four gates table’ would affect the times of all future molads, thereby changing the dates of the festivals and holy days in many more years. This proposal was also rejected.

Molad Zaqen is a strange rule to introduce into a fixed calendar based on the conjunction. If its purpose was to postpone the molad to the evening of the first possible sighting of the moon, it could have been set at 12 hours (6am), when it would still be impossible to sight the new moon on the following evening.

Two of the four postponement rules are clearly arithmetical, and Remy Landau reasons that Molad Zaqen is also an arithmetical rule.

“Dehiyyah Molad Zaqen creates considerable puzzlement and debate among scholars, some of whom have questioned whether or not it was actually rooted in R. Zera’s dictum found in the Talmud tractate Rosh Hashannah 20b. Traditional references imply that Dehiyyah Molad Zaqen has something to do with the visibility of the new moon on Rosh Hashannah, possibly over Jerusalem.

Calendar arithmetic, however, suggests a more compelling but entirely different functionality for this rule ... When Dehiyyah Molad Zaqen is removed from the calendar rules, the calculated time of the molad can be seen to exceed the first day of some months by as much as 5 hours, 23 and 4/9 minutes, which by no coincidence is exactly 6 hours later than its current maximum value.”

This dispute, however, wasn’t really about the science of the calendar, whose calculations were correct. It was about which ‘authority’ the people would follow, and whoever won the battle for power would decide which was the ‘correct’ calendar.

(to be continued)