Excerpt from my book Errors in Time (Chapter Two)
“The Hebrew calendar that Moses instituted for the Children of Israel to observe once they had entered the Promised Land was based on the celestial method of time-keeping recorded in Genesis 1:14. It had twelve months of either twenty-nine or thirty days. Adding up the days in those twelve 29-day and 30-day lunar months yielded a Hebrew year of 354 days. That 354-days in the Hebrew lunar year did not match the 365¼-day solar year that determined agricultural seasons in Israel. That was a problem since the Jewish festivals commanded by God as part of the Law were associated with the solar seasons. Thus, an adjustment had to be made to keep Israel’s lunar-based calendar aligned with the solar-governed seasons. Without some kind of adjustment (intercalation) to account for the fact that the lunar year of the Israelites was about eleven days shorter than the solar year, calendar creep would have taken place over time.
For instance, Passover was commanded by God to be a memorial remembrance of the deliverance from Egypt, to be celebrated annually in spring to mark the Exodus that took place in spring. It was to be followed by the Festival of First Fruits (Shavuot) for fifty days that was intended to coincide with the early harvest. However, the Torah-specified dates for observing both festivals, when using only a 354-day lunar-based calendar, would have caused the festivals to drift through the seasons. After three years, Passover would have been celebrated about a month earlier than the required spring observance, since the eleven day a year discrepancy, multiplied by three, equals thirty-three days. After ten years, Passover would have occurred in winter instead of spring, and a late-winter First Fruits would have taken place at a point in time when there would be no crops to harvest and celebrate. .
All ancient civilizations had to take into account the eleven-day discrepancy between a lunar-based 354-day year and the 365¼ days in a solar year. The Bible does not say anything about the pre-Exodus calendar used by the ancient Hebrews, but it was probably the one Abraham (b. 2162 BCE) brought with him from Ur III (2112-2004 BCE) when he entered Canaan in 2087 BCE. That calendar had twelve lunar months of 29 or 30 days, adjusted to keep it aligned with the solar seasons by adding a leap month every three years or so. Assyriologist Walther Sallaberger, in his study of the temple rituals of the Sumerian goddess Gula, found a contemporaneous record of the number of cattle carcasses being delivered for daily sacrifice at her temple. Some months saw 29 carcasses delivered; others had 30 carcasses. The sum of daily carcasses for an entire year was variously 353, 354, or 384.
That is strong evidence that the highly-accurate calendar used by Abraham in Ur, one that was based on the motion of the heavenly bodies, was essentially the same as the Hebrew calendar system that was given to Moses at Sinai. It is logical to assume that Abraham handed down to Isaac and then Jacob the method for keeping track of time he had brought from Ur, minus its associations with the Sumerian gods and goddesses left behind when he departed. It is also probable that the calendar of Abraham continued to be used for religious purposes by his descendants during their sojourns in both Canaan and later Egypt. More than likely, God did not introduce a new calendar to Moses on Mount Sinai but simply endorsed the sacred calendar of Abraham handed down across the centuries for use by the Israelites in the Land, explaining why no new calendar is spelled out in the Mosaic Law.
While in Egypt, though, the Israelites no doubt used the Egyptian calendar for conducting everyday business when interacting with their non-Hebrew neighbors. The ancient Egyptian calendar primarily took the agricultural seasons into account, and its usefulness required that it be reflective of the annual Nile flood as well as the motions of the heavens. It had twelve 30-day months yielding a 360-day annual cycle, but still had to be adjusted to reflect reality by adding five leap days at the end of each cycle to bring the year to an almost accurate 365 days. That the Israelites did not continue to use the Egyptian system to guide them after they left Egypt is reflected in the Law. Instead, they began using the sacred system of celestial time-keeping that God had revealed (or endorsed) to Moses as recorded in Genesis 1:14. The onlyaddition to that order being the seven-day sabbath week, which was God-ordained but not based on the motion of the cosmos.
The exact method of intercalation used by the Israelites to make their God-ordained post-Sinai lunar-based calendar align with the seasons of the equally God-ordained solar year over time is not spelled out in the Bible. A clue to how they did it is provided by the way the Babylonians adjusted their calendar, since the names of the months were the only real difference between the two calendar systems. For thousands of years, the Babylonians had known that the Earth, Moon, and Sun would align in the same relationship to each other every 235 lunar months, which they found were almost the same as the arrangement after 228 solar months. They used a repeating 19-year cycle in which there are 235 lunar months, after which the Moon’s four phases each recur in succession on the same days of the solar calendar as nineteen years before.
That same system was apparently used in ancient Israel before the Exile. Both calendars required that seven leap months be included in every 19-year cycle, a year being declared a leap year every 3rd, 6th, 8th, 11th, 14th, 17th, and 19th years to prevent calendar creep and, for the Jews, to keep Passover in the spring. That method is today called the Metonic Cycle, erroneously being credited as having been discovered by Meton of Greece circa 430 BCE more than a hundred and fifty years after it was being used in Babylon.
Notice that in all of the above discussion about the time-keeping method ordained by God in Genesis, as well as in the history of Jewish calendric usage through the ages, there is no evidence of a 360-day year being used in official Jewish circles except for a single mention in the Dead Sea Scrolls of such a critter being employed by an obscure Jewish sect. All of the evidence affirms a normal Hebrew lunar year of 354 days adjusted periodically with leap months to conform to the 365¼-day solar year over time, preventing calendar creep. So, where did the extra-biblical 360-day “prophetic year” originate? How have so many past and current expositors been misled to adopt it for interpreting Scripture? Looking back, it seems that the culprit was the desire originating in nineteenth-century England to prematurely interpret the prophecy in the ninth chapter of the Book of Daniel, ignoring the fact that God had directed the prophet to seal that book away from being understood until the time of the end.
In 1847, a year not generally recognized as the specified “time of the end” when the promised understanding of the Danielic prophecies would take place, the English Bible scholar and linguist Samuel Prideaux Tregelles (d. 1875) forged ahead anyway to popularize the use of a 360-day year for interpreting the ninth chapter of Daniel. His hypothesis was widely adopted in England and America by such Christian luminaries as Albert Barnes in his influential Barnes Notes, John Nelson Darby, C. I. Scofield in his Scofield Reference Bible, Sir Robert Anderson in The Coming Prince, Arno C. Gaebelein, Clarence Larkin, H. A. Ironside, John F. Walvoord, and Leon J. Wood, to name but a few who are well-known Bible-believing expositors that have published interpretations of the prophecies in Daniel using a 360-day “prophetic year” as the foundation for their exposition of chapter nine.12
The most powerful argument against the use of the 360-day “prophetic year” is that such a unit of time contradicts the method of time-keeping revealed in Genesis. In that book, the number of days in each of the calendar units were unambiguously ordained to be determined by the movement of the heavenly bodies. As previously explained, that movement, when monitored by ancient priests to verify the New Moon, yielded months of either 29 or 30 days, with the average over time reflecting a correct astronomical lunation of 29½ days. When the days in those twelve months are added up, the number of days in a lunar year is revealed to be 354 days, and, as far back as the time of Abraham, were intercalated with a leap month from time to time to keep the lunar calendar aligned with the solar seasons, producing a Hebrew year with 353, 354, or 383 days, but never 360 days.
The year was ordained by God in Genesis 1:14 to be determined forever by the motion of the heavenly bodies. Replacing that celestial-based year with a manmade 360-day “prophetic year” contradicts what God ordained, and using a 360-day year to expound Scripture compounds the error. Even worse, it endorses the idea that the truth of God can be set aside in favor of using the contrivances of Man.”
Check out this book in the bookstore: Errors in Time