The Origins of our Calendar


Pen Calendar1

Is the calendar that underpins God’s holy days sacred or secular? Is time “holy”?

By James McBride, The Church of God International

Almost all Sabbath-observing churches use the “Hebrew calendar” to determine when we observe the Passover and God’s holy days. Questions have arisen as to the authenticity of this calendar, and a look at its origin will help to put the various questions into perspective.

In the churches of God it has generally been assumed—though not a Jewish belief—that the calendar itself is “holy,” that it was directly inspired by God and handed down to Moses, that the Jewish authorities are charged with its maintenance. If so, it is clearly important that the calendar be properly respected and preserved. It is hoped, however, that whatever form of calendar is used, all brethren may worship together and serve our Lord God in harmony and in peace, and each follow an informed conscience.

A Measure of Time

Since man was created it has been an imperative that the passage of time be measured—e.g., for agricultural, business, government, historical, and social use. But it was also important for religious purposes. At creation God appointed the heavenly bodies to “serve as signs to mark seasons and days and years” (Genesis 1:14). The “seasons” are moed (Hebrew)—“appointed meetings,” used later in Scripture for God’s holy day appointments with His people.

There is no biblical or historical evidence that God revealed how to measure time. It was for man to discover. God gave man “dominion over the work of His hands” (Psalm 8:6)! The principle is established in the delegation to Adam the responsibility to observe and name the lower creation. So too with the measurement of time. Seth, a son of Adam, was noted in folklore for his skill in astronomy and science. He lived 912 years—long enough to observe the regular movements of the constellations and planets and to work out the pattern of the seasons! (The precession of the equinox is just one degree in seventy-two years!) By observing over time the movements of the sun, moon, and constellations, man has concocted measures of time suitable for his needs (Psalm 19:1, Proverbs 25:2).

Celestial Disturbance

Indications are that until the Great Flood in Noah’s time there was a simple regular annual pattern of twelve months, each thirty days long. This calendar can be derived from the biblical account of the Flood period (Genesis 7:11, 8:3-4).

This cycle, however, was no longer the case post-Flood, and calendar adjustments had to be made to accommodate major changes. Our year, for example, is now 365¼ days long. History records confusion, with different nations after the dispersion at Babel developing their own calendar to account for the extra days, planetary attraction, and earths newly acquired “wobble” of around three degrees. The Encyclopedia Britannica (article: “Calendar”) details the immense variety of calendars.

Calendar Origins

Perhaps surprisingly, there is no recorded controversy in the Scriptures—Old or New Testament—regarding the calendar. The sole firm calendar indicator is the instruction that the year commence in Abib—the month of “green ears,” “the earing month” (of barley) which is in early springtime. Writes C.F. Keil (Manual of Biblical Archaeology, vol.1, p. 461): “…the Law contained no regulation on the matter [of figuring the beginning of the year].”

In Egypt, however, the year at one stage was reckoned to begin with the annual overflowing of the Nile, occurring in what we would call June. Israel had, likely, been forced to adapt it during their two centuries of serfdom.

Josephus recounts that the patriarch Abraham, when in Egypt, taught the Egyptian astronomers accurate astronomy, the science that underpins the calendar (Antiquities:  Bk. 1:8:2). He learned this when he resided in Babylon. He also notes that Moses—“educated in all the wisdom of the Egyptians” (Acts 7:22)—used this same calendar when he led the tribes of Israel out of Egypt around 1490BC (Bk. 1:3:3).

The “Jewish calendar,” in other words, was widely used throughout the Middle East. “The Babylonian calendar imposed by the kings of the first dynasty [from 2000 B.C.; Abraham born c. 2166] of Babylon on all the cities immediately under their rule, was adopted by the Assyrians at the end of the second millennium B.C., was used by the Jews on their return from exile, and was widely used in the Christian era. This calendar was equated with the Sumerian calendar in use at Nippur (2300-2150 B.C.)” (Encyclopedia Britannica, article: “Calendar/Babylonian and Assyrian”).

“The Babylonian…year was sometimes twelve months long, other times thirteen months long, and the cycle repeated itself every nineteen years. This system was eventually adopted by the Semites (and the Greeks) and survives today as the Jewish religious calendar” [Charles Pellegrino: Return To Sodom and Gomorrah, p.21]. All thirteen months, using the same names as in Israel, are listed in a table of the months found at Nineveh.

The continuity of this calendar with the time before the Exodus is perhaps indicated by the precise indication given of the ages of Moses and Aaron (Exodus 7:7), and the known exact elapsed time—“the self-same day”—since their forebears had entered Egypt (Exodus 12:41). God also tells Moses to consider “this month”—i.e., Abib—the first month “of your year.” That is, the “calendar year” with its months pre-existed. The first time names for the months are noted is in Exodus 13:4, when the first month is called Abib, also called Nisan following the Babylonian captivity (Esther 3:7). Abib—“green ears”—was also the name given to this month by contemporary Canaanites.

As the Jews after the Exile (fifth century B.C.) called many of the months by Babylonian names (Nisan, etc.), it’s clear the same calendar was used there. Throughout the book of Esther, we find the same calendar in use in Ahasuerus’ empire, which stretched “from India to Ethiopia, one hundred and twenty-seven provinces” (Esther 1:1). Daniel, in Persia, used the same calendar (Daniel 10:4).

The calendar used by Moses, in other words, was widely used throughout the Gentile world from before the time of Moses and into the New Testament era—and into our day. There is no evidence that it was especially “divinely revealed” for Israel. It is a humanly devised secular calendar constantly under review by the Sanhedrin.

Changes Galore

Throughout history, intelligent vigilance has been required by all nations to properly maintain the calendar. The “Julian calendar,” supposedly—but perhaps erroneously—attributed to Julius Caesar, was found in the late Middle Ages to need adjustment, and ten days were added in 1582 (in England, in 1752, when eleven days were added) to match the calendar with the seasons. To maintain the calendar on track “leap years” were introduced, adding one day every four years. It is today called the “Gregorian calendar,” from Pope Gregory who instituted the change.

But the Hebrew calendar has stood the test of time and is seen as quite a work of genius, on a par with modern calendars! Men of Issachar were reputedly skilled in calendar calculation (1 Chronicles 12:32). They “understood the times” (Hebrew: eth­­—seasons; cf. Job 38:32). Not surprising, as calendars need constant vigilance to maintain. The Hebrew scholar Hillel II made the method of calculation of the calendar public in the mid fourth century A.D., though it was reputedly invented in the time of Simon Maccabees—c. 2 B.C.

As with all calendars, there have been occasional disputes about its accuracy—even in the time of Jesus. The Qumran community, for example, used a different calendar. Jesus never gave us an opinion on the matter. Though it’s an argument from silence, it would appear He accepted the calendar then in general use, however it was formulated by the authorities—it was not an issue with Him. There is no reason to believe He would do otherwise today, even if the calendar has been modified.

The people of Israel accepted the guidance of their authorities to regulate the times of the festivals and other calendar-dependent matters: “[A]s to the new moons and those festivals that depended on them, and indeed all other computations of time, they were committed to the care of the priests and judges, and the people were obliged to abide by their calculations, whether they proved right or wrong” (Universal History, v. 3, p.188). It was a function of the Sanhedrin—“Moses’ Seat”—a few constituent members of which were the Pharisees.

It appears that the formulation of an accurate calendar was therefore a skill that had to be learned and applied. It was not a divinely revealed calendar. That is, not “holy,” not “the sacred calendar,” not “God’s calendar,” but humanly devised, however skillfully.

Using the Calendar

Israel’s calendar has adequately fulfilled its function for thousands of years, and to this day needs only minor adjustments to maintain its function. Israelite scholars have maintained it since the time of Moses (c. 1500 B.C.).

Originally based, to some extent for symbolic religious and agricultural purposes, on annual observations, it has, as knowledge has increased, been calculated more accurately in advance for the purpose of prediction—especially of the divine festivals. A millennium before Christ, for example, in the days of King Saul—David’s predecessor— new moons were predictable (1 Samuel 20:5, 18).

Divine Plan

God uses that pre-existing secular calendar for religious purposes. To impress on mankind His plans and purposes, He has since creation had a specific pattern of festivals for man to appear before Him for worship and fellowship. Reflecting God’s overall purpose, the festivals focused on the physical harvests. Many nations, including the Canaanites, retained this original cycle of three harvest-based religious festivals—in spring, summer, autumn.

The Creator also used “physical models” to illustrate the heavenly realities. In His chosen nation of Israel, that reality was pictured by the system of worship centered on the Tabernacle and the Priesthood, and the existing calendar was adjusted to accommodate this service.

Every aspect of the true worship typified the coming Messiah, Jesus, in whom God’s purpose would be perfectly fulfilled. This divine worship was, uniquely among all religions, based on a symbolic pattern of sevens. Every seventh day is the weekly Sabbath. There are seven annual holy days, two periods of seven-day festivals, seven weeks to Pentecost, seven months of “holy day season,” seven years for the land Sabbath, and seven sevens of years till the Jubilee—and seven thousand years to complete God’s physical plan for mankind.

No “Holy Time”

All of these were placed at specific times on the pre-existing calendar—which was probably as near perfect as man could then devise. However, a totally accurate calendar is irrelevant to the purpose of God in revealing His holy day plan. He simply told Moses which month on this calendar was to be the first month of the year for religious use (Exodus 12:2): “[T]his month [it was early spring] is to be the first month of your year.”

We must note that the weekly Sabbath—also a holy day (Genesis 2:3; Exodus 20:8)—is independent of the calendar and inviolate. It is every seventh day, and history (e.g., the continuity of Sabbath among Jews, and Sunday—the “first day of the week”—among Christians) attests an unbroken link since the time of Jesus and the first Christians, who all observed the same day as their Jewish contemporaries. We can assume that the first-century observance had Jesus’ stamp of approval! Since then, the Roman calendar has had major corrections, but the weekly sequence of days remains unbroken.

Note also that Sabbath, though always “one day” for any individual, in fact lasts near enough forty-eight hours on our round earth. Brethren in Anchorage, Alaska, are beginning their Sabbath some twenty hours after brethren in Wellington, New Zealand, began theirs!

The same principle applies to all the holy days. For any one Christian, wherever he resides, the holy day lasts twenty-four hours. The “package” of sequential holy days over seven months remains intact, and overlays whatever calendar is in use. Only the lunar-solar Hebrew calendar links us to the Leviticus 23 pattern.

Anciently, when observing the beginning of a month, if no report of a new moon were reported by the thirtieth day of a month, perhaps because of atmospheric conditions, the next day was considered the chodesh, the new moon. This meant, for example, that Trumpets could be on the second day of the new moon [Keil, ibid., p. 464]. But it was still the holy day! It would also have implications for Passover. A trace of this may be seen in that today the Jews observe two days for each holy day. In 2001, for example, Rosh Hashanah (Trumpets) is September 18 and 19, though the first day is the celebration—even though it could be a day early.

The day is holy; the time is not holy!


To accommodate the requirements of Sabbath observance and divinely appointed religious ceremony, the Jewish authorities adjusted the calendar by sensible “postponements.” These, for example, ensured that the fast day—the Day of Atonement—would not be adjacent to a weekly Sabbath. Or, that there was always a full twenty-four hours from the sighting of the new moon in which to observe the Day of Trumpets. (It could first become visible during daylight hours.) The “intercalary month” is also a logical form of postponement to ensure the festivals remain in their proper harvest season. The changes were retained after the Temple service terminated in A.D. 70—perhaps to mimic and retain the Temple pattern.

Such postponements would at times have been necessary whether the calendar was “observed” or “calculated.”

However, the “postponements” are irrelevant, being merely one component of authentic calendar construction. The elements of our Christian (i.e., Roman) calendar, which is now recognized worldwide, are controlled by Papal authority. This authority has itself introduced postponements to accommodate religious practices such as Easter, and dictates when to introduce certain leap years.

It would be curious if the Jews, who were so careful about protecting the divinely revealed Sabbath and holy days, were to introduce postponements that move them away from “holy time”—even for an hour. Holy time simply does not exist!


All ancient calendars defined the passage of time by the phases of the moon. The Jews are recorded in their writings as making almost a fetish of the observance of the precise “new” moon—even though that is not specifically prescribed in the Law.

 “New moon” is chodesh, derived from a root meaning “to be new,” and is frequently translated simply as month (220 times).  Chodesh is nowhere defined in Scripture. The Jews chose to define it narrowly.

Similarly “full moon” (Hebrew: kesed, Psalm 81:3) refers to the waning moon—see 2 Chronicles 7:10 (Syriac version), where the term refers to the twenty-third of the month. However, the best translation for kesed is “in the time appointed.”

Given the potential difficulties in identifying the new moon, Keil adds: “[W]e are bound to assume that there must have been some more definite mode of determining the beginning of the months and fixing the day for the festival of the new moon, although there is no mention of it in the Old Testament” (ibid., p. 464). He cites 1 Samuel 20:5 as an example of prediction.


The Bible instructs us to “count” the date for Pentecost— that is, it is not a fixed date like the other holy days. The Jews, however, do observe this holy day on a fixed date, Sivan 6.

This in no way affects the construction of the calendar! It is an interpretation of the Bible instruction regarding the calculation of the date for the observance. Many Christian groups also interpret the text differently—some on a Monday, some on Sivan 6, the majority on a Sunday. But the underlying calendar is the same.

Calendar Quirks

The equinox can vary from March 19 to March 21. The new moon may be visible during the day. The full moon may be seen from the fourteenth to the fifteenth day since the previous new moon.

United Observance

It is essential that the specific holy days fall on the calendar in the prescribed pattern revealed in Scripture.  If our Gregorian calendar had existed, God could have placed His holy days on that just as successfully and with the same effect! What is important is the revealed pattern of worship and not our round earth’s varying position in space, which determines “time.”

Any quibbling over the calendar is counterproductive. It creates unnecessary disharmony and division among the people of God. The dates that God gave for the holy days relate to that calendar used by ancient Israel. It is a “secular” calendar maintained uniquely—there is no other like calendar widely used—by the Jewish scholars for us today along with equivalent modern calendar dates in, for example, Spier’s Comprehensive Hebrew Calendar—now available in print with holy day dates until the year 2100.

The Scriptures do not define all the parameters: a “new moon” or a full moon, spring, the length of a year, when to insert a leap month, adaptation for circumstance (e.g., Joshua 10:13, 2 Kings 20:11), etc. Such detail was “worked out” from natural events by the calendar specialists in Israel and in other nations.  The “harvest” symbolism of God’s festivals merely required that they fall in their order in the seven-month harvest sequence, with the beginning of the religious year in Abib and the holy days thereafter in their proper sequence as revealed in Leviticus 23—however the calendar was constructed.

There is no need to postulate “divine guidance” for the construction of the calendar. And there is no evidence that God did so. What’s important is that the festivals are observed from the heart and in reasonable approximation with the seasons.

We must ask: As the holy days are an important part of our faith, why would calendar matters be obscure in both Old and New Testament? If “necessary for salvation,” it would be as clear as the instruction regarding Sabbath! When we understand that the calendar is “man-made” and flexible, then there is no need for concern about the manner of its construction.

There is no advantage spiritually in deviating from what in essence is a secular calendar adapted for religious use, and used by virtually the whole of the Church of God. Saved by God’s grace, we will, however, each answer to our Judge for our Christian conduct and attitudes and not for our mathematical and astronomical prowess. An understanding of the secular nature of the calendar that underlies the holy days should remove a cause of unnecessary division among the people of God.

In Sum

The Hebrew calendar is a secular, man-made tool for the measurement of the passing of time on a round earth, and is essential for purposes of agriculture, business, social interaction, and religious observance. It alone provides a link to the holy days revealed by God using that calendar. On it are placed in sequence God’s holy-day appointments with His people, outlined in Leviticus 23, which are based around the harvest seasons. Time is not “holy”—the festival days are.

We can, in all the churches of God, confidently observe God’s holy days on the calendar which the Jewish authorities have constructed.

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