The Hebrew Perpetual Calendar, at times referred to as the Rabbinic Calendar, the Hebrew Calendar, or the Hillel II Calendar, is a calculated calendar governed by a set of rules defining Hebrew years, months, and weekdays. Historically, to calculate a date the mathematics was done by hand, an arduous process, but with the invention of the computer no longer. By the reduction of Hebrew calendar rules to a set of computer algorithms for calculating calendar dates, we all have easy access to Hebrew dates and their equivalencies in other calendar systems. A calendar converter easily provides the Hebrew dates for Gregorian or Julian dates. Our favorite converter is the Rosetta Calendar^SM.

The preciseness and accuracy of the Hebrew Perpetual Calendar in establishing the dates and weekdays in the biblical sacrificial world is phenomenal. Its exactitude self-authenticates its veracity. Consider, what is the likelihood that for years, months and weekdays the Hebrew Perpetual Calendar consistently provides its users with accurate biblical dates? Always? Often? Sometimes? Hardly ever? Does the Hebrew Perpetual Calendar follow the identical rules employed by the high priest and his associates nearly 3,500 years go?

The Hebrew Perpetual Calendar, in historical context, provides a remarkable pattern of success with respect to dating key biblical events such as the following:

• The beginning of the Israelite trek out of ancient Egypt which fell on Wednesday, March 23, 1446 BCE, Julian (at nightfall, the beginning of Nisan 15, 2315 AM).
• The tribes of Israel crossed the River Jordan into the land of Canaan on Sunday, April 4, 1406 BCE, Julian, being Nisan 16, 2355 AM.
• The fourth year of King Solomon’s reign was Hebrew year 2795 AM extending from Tishri 1, AM (September 18, 967 BCE, Julian) through Elul 29 (September 6, 966 BCE, Julian).
• The groundbreaking for the First Temple occurred on Sunday, April 14, 966 BCE, Julian (Iyyar 2, 2795 AM).
• The Day of Atonement at Ezekiel 40:1 fell on Wednesday, October 2, 574 BCE, Julian (Tishri 10, 3188 AM).

Once established, this pattern forms a prima facia case, a rebuttable presumption, for the following working hypothesis but with three caveats:

• The first caveat is that in that biblical sacrificial world, the high priest had conditional authority to invoke a one month calendar postponement of Nisan (the first month). As advised by the Calendar Council, he could add Adar II at the end of a Hebrew sacred year if cold weather had a significant adverse effect on the observance of the Passover. This involved the spring barley crop not being ready for harvest and the lambing season coming too late to meet the need for passover lambs as well as some other issues (Danby, 1933, p. 31).
• Second, in biblical times the priestly determination of the day of Pentecost was by counting 50 days, beginning with Sunday, the day after the first weekly Sabbath, during the Days of Unleavened Bread, thereby fixing Pentecost exclusively on Sundays (Josephus, Antiquities 13.8.4§252); (Whiston, 1987, p. 352); Mishna at Menanoth 10:3 (Danby, 1933, p. 506), cf. (Neusner, Mishna Yebamot, 1988, p. 754).
• Third, the Hebrew Perpetual Calendar is precise and accurate for biblical dating purposes following the deluge of Noah’s time but not necessarily before (Genesis 7-8). There were 147 days between the start of the Flood (Genesis 7) on Iyyar 17, 1433 AM (May 26, 2328 BCE) and the point “the ark rested upon the mountains of Ararat” (Genesis 8:4) on Tishri 17, 1434 AM (October 20, 2328 BCE). However, Genesis 8:3-4 suggests the grounding of the ark was 150 days from the start of the Flood. The commentaries are not particularly helpful in providing an explanation for the difference. Rather than speculating about the matter, for purposes of this analysis the veracity of the Hebrew Perpetual Calendar commences Tishri 1, 1434 just before the Ark grounded on Ararat.

For those who would argue otherwise, the burden of proof falls on those who would falsify and reject this hypothesis. The challenge to sceptics is to do so in an educated, intellectually honest, and unbiased manner.

In the biblical sacrificial world, from 1446 BCE to 70 CE, the high priest and his associates were responsible for oversight and administration of calendar matters. Unless God had provided and preserved an ecclesiastical calendar through the Levites and the Aaronic priesthood of ancient Israel, there would be no way for anyone to determine the proper date for Passover and the holydays set forth in Leviticus 23. The Hebrew Scriptures do not explain how to determine the annual point in time for the declaration of the first month in a new year. There are no explicit biblical instructions for constructing the sacred calendar. Nevertheless, the Hebrew Perpetual Calendar provides accurate and reliable dates for events in the sacrificial world of the Hebrew Scriptures and the New Testament attesting to its divine revelation as an oracle committed to the Jews for all mankind.

When the persecution of Roman emperor Constantius (337–361) threatened the very existence of the Sanhedrin, the body then responsible for officially proclaiming the molad (the birth of a new month) its president, Patriarch Hillel II, took an extraordinary step to preserve the unity of Israel. In order to prevent Jews scattered all over the earth from celebrating their own new moons, festivals and holidays at their own chosen times, he made public a fixed system of calendar calculation.

Some believe the beginning of the months were determined by direct observation of the new moon, or molad, in Jerusalem. This idea is inconsistent with the the Hebrew Scriptures. In his The Hebrew Calendar: A New Discovery, Norman S. Denham explains:

We may be quite certain that the “new moons” meant the first days of set calendar months by noting David’s words to Jonathan in I Sa. xx. 5. “Behold, tomorrow is the new moon (chodesh).” How could David have known this beforehand if the beginning of the month depended on the observation of the moon’s first appearance, and consequently upon an official proclamation it? Jonathan also referred to the new moon (chodesh) as a well known fact in verse 18. (Denham, 1952, p. 9).

If the new moons and new year were dependent on observation, then David and Jonathan could not have known in advance when a new month would begin. Setting a new month by observation was the practice of the pagan Babylonian priests not the priests of God.

The Pharisees acquired the practice from the Babylonians during the captivity and used it as a check on the calendar decrees of priests in Second Temple times. What was observed would have been the first crescent of a young moon since the new moon, i.e., the conjunction, by definition is invisible. The appearance of the young moon would be reported by the Pharisees’ witnesses to the Pharisee dominated Sanhedrin. Promoting their own authority over that of the priests, the Sanhedrin would sanctify each month (rosh hodesh) and publicly proclaimed it as if they had the God given right to do so. This rite was but an illusion for religio-political purposes.

The public ritual was inherent in the process of promotion of themselves as the spiritual leaders of then emerging Judaism. It also was a reaction stemming from the checkered history of dereliction and misconduct of the priests prior to the 586 BCE destruction of Jerusalem and the Babylon captivity. See Babylonian Chronology 626 B.C. – A.D. 75 by Richard Parker and Waldo Dubberstein (Parker, Richard and Waldo Dubberstein, 2007). The Essene answer was their own calendar and their own months.

Jesus took issue with the Pharisees’ teachings and conduct. He condemned them as hypocrites seven times in Matthew 23:13-29; cf. Matthew 6:2, 5, 16; 15:7; 22:18; Mark 7:6; Luke 12:56; 13:15). He said “you [Pharisees] travel around on sea and land to make one proselyte; and when he becomes one, you make him twice as much a son of hell as yourselves” (bracketed insertion mine); (Matthew 23:15 NASB).

Note the biting irony of Jesus’ words. He said, “all that they tell you, do and observe, but do not do according to their deeds; for they say things and do not do them” (Matthew 23:3 NASB). Contrary to what many believe, Jesus was not telling his followers to obey his critics and enemies. He was using sarcasm to say just the opposite. As to the Pharisees he said, “Let them alone. They are blind leaders of the blind. And if the blind leads the blind, both will fall into a ditch” (Matthew 15:14 NKJV). So why would Jesus tell his faithful followers to follow blind guides that would lead them into a spiritual ditch? He would not!

In any case, the ecclesiastical, or sacred, new year began in the spring. God’s instruction to Moses and Aaron was that “This month shall be the beginning of months for you; it is to be the first month of the year to you” (Exodus 12:2 NASB). The name of the first month of the ecclesiastical or sacred calendar is Abib (Exodus 13:4) meaning the month of “green ears.” Later Jews called it by the Babylonian name Nisan (Esther 3:7).

The comparison of Psalms 81:3 and 1 Chronicles 23:31 with Numbers 10:10; 28:11; 29:1 and Leviticus 23:24 show that by the luni-solar calendar of the Hebrews a new moon began the month. The terms “beginning of the month” and “new moon” are synonymous.