The Enoch calendar is an ancient calendar described in the pseudepigraphal Book of Enoch. It divided the year into four seasons of exactly 13 weeks each. Each such season consisted of two 30-day months followed by one 31-day month, and the 31st Day ended the Season. Enoch's Year consisted of exactly 364 days and the day had 18 parts per day of 80 minutes per part, which is equal to today's 24 hours per day and 60 minutes per hour, both totaling 1440 minutes per day. In order to create the 365 Day in the Julian and Gregorian Calendars, the 24 hour day was reduced to 23 hours, 56 minutes and 5 seconds, a Sidereal Day.

The Enoch calendar was purportedly given to Enoch by the angel Uriel to replace the Pentecontad calendar with its seven 50-day months.

The Enoch (Jubilee) Calendar includes 2 intercalated weeks and 4 intercalated days, specifically stating the months and the number of days in each, possibly due to emphasize a change from a 50-day month to a 30-day month and change from a seven-month year to a twelve-month year:

First month: 30 days Second month: 30 days Third month: 31 days (including the named day "Summer") Fourth month: 30 days Fifth month: 30 days Sixth month: 31 days (including the named day "Autumn") Seventh month: 30 days Eighth month: 30 days Ninth month: 31 days (including the named day "Winter") Tenth month: 30 days Eleventh month: 30 days Twelfth month: 31 days (including the named day "Spring")

It also specifically states that the four named days, inserted as the 31st day of every third month in computerized models but originally leading the following three months, would be a pitfall for kings and calendar-keepers alike because they were named instead of numbered, which "placed them outside the numbering". Just to prove the point, Enoch gives the count of 2,912 days for 8 years, which divides out to exactly 364 days per year. This specifically excludes any periodic intercalations as found in the Hezekiah Jubilee Calendar. The intercalated days in the Enoch calendar consisted of two full weeks and the four individual named days.

In order to maintain the accepted number of twelve months in a year, the number of days in each month were reduced to 30 from the original 50. The two intercalations are effected by inserting a full week at two specified intervals, the Spring and Autumn, when the Earth's orbit is longer than at the aphelion or perihelion of its orbit.

The Enoch calendar was superseded by the Hezekiah Jubilee Calendar around 701 B.C., when the shadow on the sun dial of Ahaz in the King's Garden retreated ten degrees, adding an additional 5.2422 days to the year. This same event caused the officials in Egypt to simply add the "five evil days" to the end of their calendar, as did many other nations, instead of configuring intercalations.

Many persons interested in ancient calendars are unaware of the difference between the two versions of the Jubilee calendars, as they are both referenced without the prefix of "Enoch" to indicate the earlier, or "Hezekiah" to indicate the later model. For instance, calendar expert John Pratt wrote that "The Enoch calendar has been criticized as hopelessly primitive because, with only 364 days, it would get out of sync with the seasons so quickly: in only 25 years the seasons would arrive an entire month early. Such a gross discrepancy, however, merely indicates that the method of intercalation has been omitted."[1] Pratt pointed out that by adding an extra week at the end of every seventh year (or Sabbatical year), and then adding two extra weeks to every fourth Sabbatical year, the calendar could be as accurate as the Julian calendar.


  1. John Pratt, Review of Mapping Time:, The Calendar and Its History, by E. G. Richards, American Mathematical Monthly, volume 107, number 1, January, 2000

Enoch 72:1 Book of Luminaries.

Eno. 72: 6, 11, 13, 16, 17, 19, 22, 23, 25, 27, 29, 31.

Eno. 75:1-3. Numbers were their naming convention; counting was the mathematics associated with computations.

Exodus 10:21.

See the various writings of Julian Morgenstern, James C. VanderKam and others. It is clear in Morgenstern's "The Calendar Of The Book Of Jubilees, Its Origin And Its Character"; Vetus Tentamentum, (5)1 (Jan. 1955) pp. 34-76 that he is unclear of the structural differences between the Pentecontad and the Jubilee models, however.

"Cycle of Priestly Courses from Calendrical Documents 4Q320 and 4Q321." Retrieved 12/15/2000 from

"Sabbatical Years and the Year of Jubilee". Sidney B. Hoenig; The Jewish Quarterly Review, New Series, Vol. 59, No. 3 (Jan., 1969), pp. 222-236.

"A Possible Method of Intercalation for the Calendar of the Book of Jubilees". E. R. Leach; Vetus Tentamentum, Vol. 7, Fasc. 4 (Oct., 1957), pp. 392-397.

"Jubilee Calendar Rescued from the Flood Narrative". S. Najm & Ph. Guillaume. Retrieved 6/22/2008 from

"Sabbatical, Jubilee, and the Temple of Solomon." L. W. Casperson. Vetus Testamentum, Vol. 53, No. 3, 2003, pp. 283-296(14).

"Calendars of the Dead_sea-Scroll Sect". Edward L. Cohen; CUBO Mathematica Educacional; Vol. 52 No. 2, (1-16). Junio 2003.

Biblical Calendars. J. van Goudoever. Leiden, E. J. Brill, 1959.

"Tracing the Origin of the Sabbatical Calendar in the Priestly Narrative (Genesis 1 to Joshua 5)". Philippe Guillaume. Retrieved 6/22/2008 from

"Studies in the Hebrew Calendar: (Interpretation of a Difficult Passage in the Palestinian Talmud)". Solomon Gandz. Proceedings of the American Academy for Jewish Research, Vol. 17, (1947-1948), pp. 9-17.

"Chronology of the Account of the Flood in P.--A Contribution to the History of the Jewish Calendar. Benjamin Wisner Bacon. Hebraica, Vol. 8, No. 1/2 (Oct., 1891 - Jan., 1892), pp. 79-88.

"The Calendar of the Book of Jubilees, Its Origin and its Character." Julian Morgenstern. Vetus Testamentum, Vol. 5, Fasc. 1 (Jan., 1955) pp. 34-76.

"The Judean Calendar during the Second Commonwealth and the Scrolls." Solomon Zeitlin. The Jewish Quarterly Review. New Series, Vol. 57, No. 1 (Jul., 1966), pp. 28-45.

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