Bible Calendar Part 2

Table of Contents

The biblical calendar determines the start of the new year

Graphic of vernal and autumnal equinoxes
Vernal & Autumnal Equinoxes

Can the sun, moon, and stars alone show us when to start each year? We saw in Bible Calendar Part One that the first rule tells us when each day of the week begins, so we can count the days to each weekly sabbath. The second rule tells us when the first day of each month has begun. We number the days in the month to determine when to observe each annual festival. But the third rule is needed to tell us when the first month of the year begins, the month in which Passover and the days of Unleavened Bread are observed. Six months later, in the seventh month of the year, all the fall festivals occur. Genesis 1:14-19 says that the sun, moon, and stars are for “signs, and for seasons, and for days, and years” (KJV). This covers everything a calendar has to do.

Genesis 1:14 states that the light of the sun, moon, and stars is to be used to determine years. In some very simple way, the start of each year can be known by observing only the light of the sun, moon, and stars. If anything else were needed, Genesis 1:14 would not be true. Does the Bible give us enough information to know how this should be done?

“And the LORD spoke unto Moses and Aaron in the land of Egypt, saying, This month shall be unto you the beginning of months: it shall be the first month of the year to you.” (Exodus 12:1-2, KJV)

In Ex. 12:2, we see that God told Moses and Aaron that that month would be the first month of the year. Then they were given instructions about what to do on specific days of that month. They did not need to be told which day of the month that day was. They knew already, because they had seen the new moon on the first day of the month.

We know that this was a spring month, since the state of the crops is given in Ex. 9:31-32. The annual flooding of the Nile is caused by monsoon rains in Ethiopia, and comes in late summer. At one time the Egyptians used a lunar calendar beginning with the late summer flooding of the Nile. Later, they used a “wandering” calendar of 365 days, which moved backward through the seasons one day every 4 years, or one full year in 1460 years. The four “seasons” in that calendar were named according to conditions in Egypt, the first months originally being in the season named for the late summer flooding.

It is not known when the change of calendars was made in Egypt, but there is reason to believe that it may have been about the time of the Exodus. In 1489 BC, the most likely year for the Exodus, the start of the Egyptian year in the 365-day calendar would have been at the same time as the annual flooding.

Whichever calendar was used by the Egyptians at the time of the exodus, their year began in August or September. That would be why Moses and Aaron had to be told which month would be “the first month of the year to you“, not late summer, but spring.

In any case, Moses was certainly using a lunar calendar, or else God would have needed to tell Moses and Aaron (Ex. 12:2) which day of the month it was, in addition to telling them which month would start the year. They were told to give instructions to the people (Ex. 12:3) using dates in that month. There is no indication that the people needed to be instructed in a new calendar. The people already knew which day of the month it was. In Ex. 12:2 Moses quotes God as using the word chodesh for month. This word means “new”, and refers to the visible renewing of the moon. Also, he had lived for 40 years in the land of Midian, where he would have been using the same kind of calendar used then all over that part of the world, and that was invariably lunar-based.

“While the earth remaineth, seedtime and harvest, and cold and heat, and summer and winter, and day and night shall not cease” (Genesis 8:22, KJV).

The account in Exodus shows that it was already springtime in Egypt when Moses and Aaron were told which month would be the first month of the year. Winter had ended, and a new year had begun. Winter in the northern hemisphere ends when the sun crosses the celestial equator on its annual path from south to north against the fixed stars, as seen from the earth. This is called the vernal equinox. “Vernal” means “spring.” The vernal equinox marks the change from winter to spring.

Each year in a lunar based calendar consists of whole months. The calendar used by Moslems has 12 months every year. Since 12 months is less than one solar year, that calendar slips backward about 11 days each year, with respect to the seasons. But the calendar revealed in the Bible is different.

We know by biblical statements and examples that every year consists of whole months, with at least 12 and sometimes 13 months. There is an example of a 13-month year in the book of Ezekiel. Ezek.1:1-2 says Ezekiel began to see visions and receive instructions. It was the 5th day of the 4th month of the 5th year of the king’s captivity. At least 7 days passed (Ezek.3:13) before he received a special instruction which would take 430 days to perform (Ezek.4:4-6).

This instruction had already been performed by the 5th day of the 6th month of the 6th year (Ezek.8:1). So from the 4th month of one year to the 6th month of the next year (same day of the month) at least 437 days had passed. If the 5th year were a 12-month year, this would be only a 14-month period. Even if every month had been 30 days, this could only be 420 days (14×30). So the 5th year of king Jehoiachin’s captivity must have been a 13-month year. A 13-month year plus 2 extra months would be at least 441 days. The 437-day period had ended before the 15 months ended.

The reason for adding a 13th month in some years is to keep the calendar in accord with the seasons. With this system, the start of each year should always be within a 30-day range with respect to the seasons.

Since each year consists of whole months only, each year has to begin at the start of a month. The start of each month is determined by the moon. Which month starts the year is determined by the sun. As the seasons change throughout the year, the path of the sun changes. As seen in the northern hemisphere, the sun rises and sets farther south every day in the fall, until the winter solstice (about Dec. 21) when it is as far south as it gets. This is the first day of winter. In spring it rises and sets farther north every day until the summer solstice (now about June 20) when it is as far north as it gets. This is the first day of summer.

In between the two solstices are two equinoxes: the vernal equinox, marking the first day of spring in the northern hemisphere (about March 21), and the autumnal equinox, marking the first day of fall (about Sept.22). At the time of an equinox the sun rises and sets midway between the two extremes (the two solstices). The sun’s course across the sky on those days is directly above the earth’s equator. It is perhaps surprising to learn that wherever you are on earth, these midpoints are always in the same place on the horizon. On the day of the equinox, the sun rises due east and sets due west – no matter how far north or south of the equator you are. On the equinox, the night and the day are of equal length. (It differs slightly from this ideal because of atmospheric refraction.)

What the Jewish captives in Babylon remembered

In 1956, a small book was written by Richard Parker and Waldo Dubberstein, called “Babylonian Chronology 626 B.C. – A.D. 75.” It was published by Brown University Press. It is still available in college libraries, and photo reprints can still be purchased. This book contains information about the calendar used in Babylon during those centuries, based on clay tablets with cuneiform writing. Many dated documents exist from those centuries, so many that documents dated during “intercalary” months can show, in almost every case, which years had an extra month – either an extra Ululu, the 6th month, or an extra Addaru, the 12th month.

During the 7th and 6th centuries BC, the calendar used in the Babylonian empire was regulated by the astronomers of the day, who were actually astrologers. They would notify the king when an extra month was needed to keep the calendar in line with the seasons, and a notice would go out in the king’s name to each district.

A study of this information has revealed some surprises. During the reign of Nabopolassar, the father of Nebuchadnezzar II, the calendar was not well regulated. Between 626 BC and 605 BC, “intercalations” were made in such a haphazard manner that in the year 607 BC, after three years in a row of 12 months each (not possible in a well regulated calendar) the new year started 22 days before the spring equinox. Just 2 years later, it started 15 days after the equinox. That is a range of 37 days. The range should not be more than 30 days. Of 22 years, 12 began before the equinox, and 10 after. The average start for Nisanu, the first month, was one day before the spring equinox.

It might appear that what they were trying to do (and not very well) was to start the year with the new moon closest to the equinox. But a study of the starts of the month Tashritu, usually the 7th month, shows that it is likely that what they were actually trying to do was to regulate the start of that month instead. They were more successful at that. The earliest start for that month was 20 days before the autumnal equinox, and the latest was 13 days after. That is a range of only 33 days, much closer to the ideal of 30 days, with the average start for that month about 4 days before the fall equinox. Perhaps they had reason to delay the start of that month if the summer harvest was not yet completed.

Whatever the astrologers may have been trying to do with the calendar during the reign of Nabopolassar, we find that during the reign of his son, the famous Nebuchadnezzar, the calendar was radically different. Nebuchadnezzar began to reign in 605 BC, and during his second year, in 604 BC, he conquered Jerusalem and carried away to Babylon many Jewish captives, including Daniel.

After 600 BC, which had a second Ululu, nearly all years started after the equinox. 31 of the next 34 years started after the equinox. The earliest, 584 BC, started 5 days before the equinox. The average start for these 34 years was 13 days after the equinox. This is 14 days later than the average year started during the reign of Nabopolassar. That is a major change in the calendar. Why? What had happened?

The Bible has the answer. In the second year of Nebuchadnezzar’s reign, the king had a dream which only Daniel could interpret. As a reward, the king made Daniel ruler over the whole province of Babylon (Daniel 2:48) and chief of the governors over all the wise men of Babylon. Who were the “wise men” of Babylon? They were the “magicians, and the astrologers, and the sorcerers, and the Chaldeans” (Dan. 2:2). We know this because in Dan. 5:11, the queen says to Belshazzar that Daniel was a man whom “the king Nebuchadnezzar thy (grand)father … made master of the magicians, astrologers, Chaldeans, and soothsayers.”

This was said about 65 years later. Except when Daniel was being thrown into a lion’s den, or otherwise treated badly by the king, for many of those years he was telling the astrologers how to do their job. It was Daniel who was regulating the Babylonian calendar. And what was the first thing he did? When it was in his power to do so, he began to make sure that each year started after the spring equinox!

In Babylon the year was always based on lunar months, and from Daniel’s time on, the first month almost invariably started after the vernal equinox (in spring). At first, a second “Ululu” ( the 6th month) instead of a second “Addaru” (the 12th month) was often added, as had been the custom. This practice would not have affected the observance by the Jews of the holy days in the 7th month, as it would still be “the 7th month”, regardless of its name (Lev. 23:24). Sometimes an intercalation was missed, and a year would be allowed to start early. They experimented with an 8-year cycle for a while.

Eventually, a 19-year cycle was instituted, after which no year ever started before the equinox. This cycle still used a second “Ululu” (the 6th month) for one of the 7 extra months in each cycle. That particular year in each cycle was the one in which the month Tashritu would have come earliest in the season. So delaying Tashritu if it would start too early was still a feature of that system, while also guaranteeing that each Nisanu, the first month, would start after the vernal equinox.

Starting years in the spring was still the practice when the books of Ezra and Nehemiah were written. Also Haggai and Zechariah. These books all refer to years numbered according to the regnal years of kings in Babylon, or the Persian kings who ruled it, and adopted the same calendar. See Esther 3:7. Those years always started in the spring.

The calculated calendar used now no longer starts the year with the first month after the vernal equinox. The day that starts the seventh month is now called “Rosh Hashanah.” This phrase means “the head of the year” or “the beginning of the year.” But when that calendar was first used, some time after the destruction of the temple in the year 70, and before the calculation was disclosed in the year 358, the first month was still seen as the start of the year.

That calendar was originally designed to use a 19-year cycle which would assure that each year would start with the first month in which the 16th day would be on or after the spring equinox. Even the 14th of Abib, the passover, could then have come before the equinox, in winter. This would have put the start of the year one month earlier than the Babylonian calendar for about half of all years. Some people today have decided to start years with the new moon closest to the equinox, either before or after it. This could not have been the calendar that Daniel and the other Jews remembered from before the captivity, since half of all years would start a month earlier than the Babylonian year did while Daniel was in charge of the calendar there.

During the Captivity the Jews began to use the Babylonian names for the months. Since they already had a year with numbered months starting in the spring, if their year had been started by a different rule than was used in Babylon, with many years starting a month earlier, they would have continued to use numbers for the months in their own calendar, or the old Hebrew names. They could not have adopted the Babylonian names, since they would not match from one year to another, if their own calendar were that different.

But the biblical record shows that Daniel himself was in charge of the Babylonian calendar. If the calendar remembered by Daniel and the other Jews in captivity had not started all years after the equinox, Daniel could have made Babylon’s calendar match whatever system may have been used. Why would he institute a new system for Babylon which started every year after the equinox, if all the Jews were using a different calendar that often started years sooner? The Babylonians themselves had let the calendar slide back half a month anyway. If that had been the practice in Judah, Daniel could have left it that way.

We have several references to the numbers of the months, such as Esther 2:16 and 3:7, Zech.1:7, 7:1. These numbers match the numbers used today. We also find 4 of the old names. The first month, Abib, in Ex.34:18. The 2nd month, Zif, in I Kings 6:1. The 7th month, Ethanim, in I Kings 8:2. The eighth month, Bul, in I Kings 6:38. These names refer to the change of seasons, so we know they began in the spring. Abib, the first month, refers to the ears of barley in April. Zif refers to the brightness of flowers in May. So we can conclude that the religious year followed one simple rule – start the year in spring, not in winter.

We know that a civil year, fall-to-fall, was once used in ancient Judah, which began in the 7th month and ended in the 6th month. But the numbers of the months always reflected a year starting in spring. The extra month was intercalated after the 12th month. They may have begun again to use this civil year in the days of Nehemiah (Neh.1:1 and 2:1) to number regnal years (years of a king’s reign). (We know that the Jews living at Elephantine, in Egypt, during the fifth century BC were sometimes numbering regnal years this way.) But they were not doing it that way when the book of Haggai was written, 60 years earlier. Compare Haggai 1:1 and 2:10.

This practice shows that the Jews of Nehemiah’s day, a century after Daniel’s time, had not simply adopted the Babylonian calendar, but were very deliberately using their own calendar, the one they remembered from before the captivity. When they had their own local government again they resumed their own civil calendar, but with the month names now Hebrew forms of the Babylonian. They were able to use the Babylonian month names because their own calendar also started the “religious year” after the spring equinox, when the Babylonians were now starting their years. The first month was always in spring, and the Feast of Tabernacles was always in the fall.

There was also an agricultural year, that ended after the summer harvests, related to the Sabbatical years and Jubilee year. That year was proclaimed on the Day of Atonement (Lev.25:9), the tenth day of the seventh month, not on the first day of the month. It began at the end of the actual harvest, and at the end of summer. When the 16th chapter of Deuteronomy was written, the summer harvest was expected to be over by the start of the Feast of Tabernacles on the 15th (Deut.16:13). Leviticus 23:39 states expressly that the fruit of the land would be gathered by the 15th day of the 7th month. So that day has to come after the summer harvest is completed. The counting of agricultural years from the 10th of the 7th month may have been the reason for using a civil year beginning on the first of the same month. Agriculture was the basis of their economy.

Determining equinoxes by observing the sun

Graphic image of equinoxes

It was the season, then, the vernal equinox itself, that had been used by the Jews before the captivity to determine when each year started. Noah knew when the new year had started while still in the ark. When the Israelites were wandering 40 years in the wilderness they had no way to know about barley crops in Palestine. But Moses did know how to determine the equinox. He was an educated man. If there were a simple method to find the day of the vernal equinox, a method that does not require years of observations or complex calculations, it would show that the sun alone can be used to tell which is the first month of the year.

It is not difficult to determine when the equinox comes, with an accuracy of one day. Here’s how:

  1. On a plain with a clear view of both east and west horizons, set up a post or stone to sight the rising sun from.
  2. At sunrise have someone set up another marker (the East marker) at a known distance, to show the place where the sun rises.
  3. At sunset the same day have your assistant set up another marker (the West marker), to show where the sun sets, and at the same distance from the sighting point.
  4. For more exactness, adjust the sunrise marker (the East marker) the next morning to the average of the two sunrises.
  5. Those 2 markers are now on a line due east and west of each other. Use them to determine the day on which the sun rises due east and sets due west. The observation point in step 1 is no longer needed.

NOTE- This simple method could have been used to align the pyramids at Giza with the four compass points, centuries before the time of Moses.

This method is very accurate, as long as the true horizon can be seen. (Mountains to east or west would have to be compensated for.) If done carefully, there will be no more than a one-day error. In nearly all years it works well enough to tell if a month starts before or after the equinox has occurred. At the latitude of Jerusalem, in the days near the equinoxes, the place where the sun rises or sets changes (in steps) just under one half degree each day. This is about the width of the sun, so it is not hard to get enough accuracy. Atmospheric refraction causes a half degree of “error,” so the “actual” spring equinox may be one day later, the fall equinox one day earlier than the observation.

At the latitude of Scotland, the daily step is three fourths of a degree, and the refractive error nearly one degree. This method would also work near the equator. Even at the equator, the sunrise and sunset points move north and south with the seasons. But there, the sun, moon and stars always set straight down to the horizon, at nearly a 90 degree angle, so there is no refractive shift. The observed day is the true equinox.

Once you have determined the time of equinox carefully, after that it can be determined every year by observing the rising or setting of prominent stars, since this changes nightly. This was how the precession of the equinoxes was discovered. It works anywhere, and works well if careful observations are made. Noah could have used this method on the ark. The precession of the equinoxes is so slow that a careful observation of prominent stars on the night of the equinox can confidently be expected to repeat every year for decades. The precession of the equinoxes is only one degree in 70 years. So observing only the stars every year to determine the equinox would not lead to an error of a full day until nearly 70 years had passed.

When the 13th month starts, if the equinox has not yet come, it is still winter. It is a winter month, and the last month of the old year. If, when the 13th month starts, the equinox has already come, it is spring. So it is a spring month, and that month is the first month of the new year. In most years, it isn’t even close. If the sun has just set north of the east-west line, spring has started. If the sun has just set south of the east-west line, it is still winter. This observation can be made anywhere, by anyone. We don’t start a new day until the old day is ended. We don’t start a new month until the old month is ended. We don’t start a new year until the old year is ended. If it’s still winter, the old year hasn’t ended.

Is that all there is to it? Could it be that simple? After 12 months of the year are completed, if the next month starts before the vernal equinox, it is the 13th month of that year. If it starts after the equinox, it is the first month of the next year. How could it be that simple? If it were that simple we wouldn’t need a priesthood to interpret the rules, and experts and teachers to pass on the secret knowledge by oral tradition, and rulers to make decisions and issue edicts. We wouldn’t need 19- year cycles. We wouldn’t be using postponements, or planting barley, or counting backward from the seventh month. It is that simple, and we can prove it from history and the Bible.

Two equinoxes – Two types of year

Nowadays, of course, we can know the exact moment of the equinox, because it can be found in any almanac. Or, we can choose to observe it for ourselves. If the new moon is seen before spring begins, it means that it is still a winter month. Even though most of the month may be in spring, it is the start of the month that counts.

There is a surprising connection between the two equinoxes, spring and fall, and the two types of biblical year, religious and agricultural.

It is a direct relationship between the start of the religious year in spring, and the start of the agricultural year, in fall. It is shown by the fact that the agricultural years (including the sabbatical years and jubilee years) do not start on the first day of the seventh month, but instead start on the tenth day of that month, the day of Atonement.

The fall equinox comes about 186 days 10 hours after the spring equinox every year. The Day of Atonement, the day that starts the Jubilee years, and each agricultural year (See Lev. 25:8-13.), comes either 185, 186, or 187 days after the first day of Abib. When the earliest possible first month starts on the first day after the spring equinox, the Day of Atonement is most likely to be the first day after the fall equinox. Of course, in most years the Day of Atonement comes well after the equinox, because the first month starts well after the equinox. This guarantees that the whole Feast of Tabernacles, starting five days later, will always occur when summer is over.

This relationship is not just an accident or a coincidence. While it gives no absolute guarantee that the Day of Atonement itself will always be after the very end of summer, it is instead evidence that both types of year are related directly to the equinoxes, and to the seasons of the year. Notice that 186 days, the time from the first day of the religious year to the first day of the agricultural year, is not just half of a solar year, which is less than 183 days, but is instead, as nearly as possible, the exact length of time between the spring equinox and the fall equinox.

Each year then, these two types of year bear the same relationship to their respective equinoxes. If the one starts, for example, 20 days after the spring equinox, the other starts 20 days after the fall equinox (within one day). Notice that this relationship is from the first day of Abib, not from the passover or the wave sheaf offering. It is the first day of the first month that has this relationship to both equinoxes.

The year 2026, if determined by observation at Jerusalem, will be one of those very unusual years when the first of Abib starts just after the spring equinox, and the day of Atonement ends just before the fall equinox. When starting each year after the spring equinox, it is extremely rare for the Day of Atonement to come this early. But the Feast of Tabernacles could never do so. It is the 7-day Feast of Tabernacles that the Bible requires to start after the autumnal equinox.

What about the barley?

Consider this point. God tells us plainly to use the light of the sun, moon, and stars to determine the start of each year (Gen 1:14). But at the same time He required a wave sheaf offering on the day after the sabbath during the days of Unleavened Bread, and this needed barley from that year’s crop. While the new crop could be harvested before the wave sheaf offering (See Lev. 23:10.), it could not be eaten until then. (See Lev. 23:14.)

The time of the wave sheaf offering, then, ought to be at about the same time of year as the barley harvest starts. That is to say, the average time of the offering should be at the average time that barley ripens in Palestine. It must allow for variations in the ripening of the barley, and also for the natural variation in the start of a year, with reference to the equinox. Every year the end of the 12th lunar month is about 11 days earlier in the season than the end of the previous year. No matter what system is used, there will always be a 30-day range for the start of the first month, and thus a 30-day range for the wave sheaf offering, in terms of the solar year and the seasons.

Would God have required a wave sheaf offering during the first month without making certain that fully developed barley would always be available for it, over the full 30-day range? Yet He says that the sun, moon and stars are to be used to determine the year, not the barley harvests. How can this be?

Bible Calendar Part Three of this article explains why it is not necessary, and not required, to observe the ripening of barley – the solution to the “wave sheaf problem.” It also explains in more detail why the first day of the first month must be in the spring, and not just the day of the Passover or the day of the wave sheaf offering. This is shown from an historical and agricultural perspective, as well as with biblical evidence. It will be shown why the Feast of Tabernacles is supposed to start in the fall, after the “autumnal equinox.” Finally, part three deals with what the historical record shows regarding the history of the calendar, and how and why changes were made in the calculated calendar over many centuries.

Creative Commons License NonCommercial-Attribution-No Deriviatives.
Credit Derek G. Davies with a link to

Written by Derek G. Davies. Dated Sept. 22, 2002.
Edited June 2005 and March 2013.