The Hebrew calendar is a solar-lunar calendar which begins the counting of years (with year 1AM) in the autumn of 3761BC. It is calculated using ancient formulas to predict the movements of both the sun and the moon. Over thousands of years, these calculations continue to produce a calendar in close proximity with the natural lunar cycles and the annual harvest seasons. Whether temporary alterations in the courses of the celestial bodies in the days of Joshua (Josh. 10:12-13) and Hezekiah (2 Kings 20:8-11) had any significant impact on the timing of the new moons (requiring an adjustment in the calendar) is not known. For this and other reasons it is not possible to verify the accuracy of the Hebrew calendar (as calculated here) in ancient times. Although approximately correct, it may differ by a day or two – or in some years by a month from what was actually observed, based on such things as the timing of the barley harvest and the practices used for defining the commencement of months. The calculated Hebrew calendar displayed at this web site is known to match what has been in use by the majority of the Jews from the time that the rules of calendar calculation were made public in the fourth century AD. These rules (carefully guarded by the priesthood and with adjustments to keep everything in its proper season) were apparently in use for many centuries before that. The scriptural evidence is that Moses was instructed in the use of the Hebrew calendar (Ex. 12:2). And the 3761BC date of origin indicates that methods for calculating this calendar may have first been understood in the days of Seth when "men began to call upon the name of the LORD" (Gen. 4:26). This is in harmony with the claim of Josephus that Seth’s children (presumably with Seth’s involvement) "were the inventors of that peculiar sort of wisdom which is concerned with the heavenly bodies, and their order" (Antiq. 1.2.3).

The calendar in common usage in the Western world today is a solar calendar without any correlation to the movements of the moon. It is a Roman calendar based on the one established by Julius Caesar in 46BC. Augustus Caesar later borrowed a day from the month of February to make the month named after him just as long as the one named after Julius. He also rearranged the lengths of the three months after August. With these slight modifications by Augustus Caesar, the 365¼-day Julian calendar continued in use without further modifications until the time of Pope Gregory XIII. The Gregorian calendar, established by Pope Gregory in October 1582 adjusted the calendar to stabilize the dates of the equinoxes and solstices, and to compensate for the 10-day drift of the vernal equinox away from the date on which it had occurred in the year of the Nicene Council (325AD). Gregory’s revised calendar was readily accepted by the Catholic European nations, but was met with resistance elsewhere. The Germanic states finally accepted it in 1700. It was adopted by the English in 1752, by the Russians in 1918, by the Greek Orthodox Church in 1923, and by the Turks in 1928.

The Roman calendar on this web site is the Gregorian calendar from 1582 to the present and beyond. Prior to 1582, it is the Augustan version of the Julian calendar. In other words, it is not accurate for dates in Protestant countries from 1582 until they changed to Gregorian counting. Nor is it accurate for any time before the reign of Augustus Caesar. (The calendar of Julius Caesar was only slightly different than what you will find here. Prior to that the Roman calendar varied greatly, and any "Roman" dates illustrated for such years are purely hypothetical.)

All the days on which special offerings were established in God’s law (over and above the daily and weekly offerings) are highlighted in yellow on these calendars. Highlighted in blue are additional festivals and fast days mentioned in the Bible – days voluntarily set aside by the Jews in commemoration of events in their national history. Scriptural references to these dates are listed below (with festival scroll readings in Italics):

*With the exception of the Day of Atonement, whenever a fast day falls on the seventh day of the week, its observance is shifted to maintain the holiness of the Sabbath day. (This is in accord with the scriptural admonition and example found in Nehemiah 8:9-12; 9:1). If a fast day occurs on a Saturday, it is postponed to Sunday except for the Fast of Esther, which is moved back to Thursday due to Purim.