It is vital that, if we are to correctly understand the precision of biblical prophecy, we must determine the precise length of the biblical (or prophetic) year which is used in Scriptures.
Our modern word calendar is based on the solar cycle, and consists of 365.25 days. The modern Jewish calendar is calculated according to both the lunar and solar cycles. Their twelve months are currently calculated as containing 354 days, which leaves their year eleven-and-one-fourth days short of the true solar year. This is corrected by adding a "leap month," known as Ve-Adar, seven times during a nineteen-year cycle.
However, when we turn to the Scriptures we discover that the biblical-prophetic year consisted of 360 days. Abraham, the father of Israel, continued to use the 360-day year, which was known in his home in Ur of the Chaldees. The Genesis account of the flood in the days of Noah illustrated this 360-day year by recording the 150-day interval till the waters abated from the earth. The 150 days began on the seventeenth day of the second month, and ended on the seventeenth day of the seventh month (Genesis 7:11,24 and 8:3-4). In Other words, the five months consisted of thirty days each; therefore, twelve months would equal 360 days (12 x 30 = 360 days).
Sir Isaac Newton stated, "All nations, before the just length of the solar year was known, reckoned months by the course of the moon, and years by the return of winter and summer, spring and autumn; and in making calendars for their festivals, they reckoned thirty days to a lunar month, and twelve lunar months to a years, taking the nearest round numbers, whence came the division of the ecliptic into 360 degrees." ( Anderson, Robert. The Coming Prince. London: Hodder & Stroughton, 1894. )
The truth about the biblical 360 day year as mentioned by Newton was quoted by Sir Robert Anderson in his book, The Coming Prince, page 68. This was not a new discovery by Sir Isaac Newton in the late 1600's or even by Sir Robert Anderson in 1895. It was clearly discussed in detail by Christian, Julias Africanus in his Chronology in his explanation of the fulfillment of Daniel's Seventy Weeks, written about A.D. 240.
The book of Esther (1: 4) indicates the same 360-day length of year by recording the six-month-long feast of Xerxes as continuing exactly 180 days.
The Prophet Daniel recorded that the time of the absolute power of the Antichrist over the nations will last three-and -one-half years (Daniel 7:25). John, in the book of Revelation, described this same three-and-one-half year period (Revelation 13:5-7) as consisting of forty-two months of thirty days each, totaling 1260 days (Revelation 11:2-3; 12:6). The biblical writers used the ancient 360-day biblical year in both the historical and predictive parts of Scripture.
Reference: Jeffrey, Grant R., "Armageddon, Appointment with Destiny", Frontier Research Publications, Inc. (1988), p.221-224
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