[Excerpt from Chapter 7: When Will Jesus Die? Daniel 9]
When we add 483 years to 444 B.C.E., we find that Daniel predicted the Messiah would die in 39 C.E. While this is close to the actual date of Jesus’ death (33 C.E.), it isn’t exact. If God was really predicting the death of Jesus, wouldn’t we expect him to be perfect in his prediction? What else should we expect from an all-knowing Being?
As it turns out, we forgot something.
Daniel (and the ancient Jews) didn’t use our modern calendar system.
The Gregorian calendar wasn’t adopted until the end of the 16th century. In Daniel’s day, our calendar wasn’t even invented yet. Of course, we would never assume that ancient people had our scientific or medical knowledge. Why would we ever assume that they had our chronological knowledge or measurements? They simply didn’t use our solar calendar back then. Therefore, we shouldn’t use our calendar system in determining this prophecy; instead, we should look to the Bible and find their calendar system. When we investigate this, we find that the Jews used a 360 day calendar.
Religiously, we see that the Jews structured their worship around the “new moon” calendar (Ps. 81:3; Num. 29:6; 1 Sam. 20:5; 1 Chron. 23:31; 2 Kings 4:23; Ezek. 45:17). Elsewhere we read that the Jews counted time according to the cycles of the moon (Ex. 19:1). Widows were given a “full month” to mourn for their husbands (Deut. 21:13), and likewise, the book of Numbers explains that the people mourned over Aaron for “30 days” (Num. 20:29).
Historically, in the book of Genesis, we read that Noah equated 5 months to 150 days (Gen. 7:11; 8:3-4).
Prophetically, the apostle John (a first century Jew) equated the 42 months of the tribulation (Rev. 11:2; 13:5) with 1,260 days (Rev. 12:6; 11:3). Alva McClain concludes, “It is clear that the length of the year in the Seventy Weeks prophecy is fixed by Scripture itself as exactly 360 days.”
Finally, culturally, other ancient nations used a lunar calendar—not a solar calendar. For instance, according to the World Book Encyclopedia, the Babylonians used a lunar calendar (354 day year), and at one point, the Babylonians had invaded and occupied Israel. When Daniel made his prediction, he had just recently left Babylonian occupation. Therefore, it’s likely that the Jews used something similar to the Babylonian calendar. While scholars do debate this, it seems likely that these nations would have influenced the Jews in their calendar system before the time of Christ.
Does this mean that their calendar would get thrown off over the course of a few decades? Not at all. The World Book Encyclopedia writes that an “extra 29-day month is inserted between Adar and Nisan” to keep the calendar from shifting. However, Jews did this retrospectively—not prospectively. In other words, when they looked into the past, they corrected their calendar; however, they didn’t do this when they looked into the future (as we see in Revelation 11:2 and 12:6). Therefore, when Daniel predicted 483 years, he was referring to 360-day years.
 McClain, Alva J. Daniel’s Prophecy of the Seventy Weeks. Grand Rapids, MI: Zondervan Publishing House, 1969. 22.
 The World Book Encyclopedia 1985. Chicago: World Book, 1985. 28.
 Finegan writes, “The supposition is, therefore, that the Israelite calendar is originally lunar, with close relationship to agricultural and climatic factors, and that as it was harmonized more accurately with the movements of the celestial bodies it was primarily the relationship to the sun that was kept in view; thus the calendar became lunisolar.” Finegan, Jack. Handbook of Biblical Chronology: Principles of Time Reckoning in the Ancient World and Problems of Chronology in the Bible. Peabody, MA: Hendrickson, 1998. 32. However, while they both hold to a lunar year, both the World Book Encyclopedia and Finegan argue that this lunar calendar was based on a 354 day year. Likewise, Julius Africanus (a Christian apologist) writes that the Jews operated off of a lunar calendar, but he also believed that this was 354 days long. Tanner writes, “The Jews, [Africanus] said, reckoned a year as 354 days rather than 365 1/4 days. The former represents twelve months according to the moon’s course, while the latter is based on the solar year. This amounts to a difference of 11 1/4 days per year but is eventually made up by the insertion of extra months at eight-year intervals. Tanner, J. Paul. “Is Daniel’s Seventy-Weeks Prophecy Messianic (pt.1)?” Bibliotheca Sacra. Volume 166. April-June, 2009: 191-192.
Does this defeat the assertion that the Jews operated on a 360 day year? I don’t think so based on the evidence above. However, even if the Jews did use a 354 day year, then this would still bring us to roughly 25 C.E. for the fulfillment of Daniel 9. This could very well predict the beginning of Jesus’ ministry, rather than the end of it. Of course, Robert Newman has used a calculation called “sabbatical cycles” which brings us to the years C.E. 27 to 34 for the final cycle. Therefore, it’s possible that the 354 day model could be accurate, as well. For a summary of his calculation, see Newman, Robert C. “Daniel’s Seventy Weeks and the Old Testament Sabbath-Year Cycle.” Journal of the Evangelical Theological Society. Journal 17. Issue 4. 233-234.
 It seems that the Jews switched over to a solar calendar at some point, but the earliest sources for this occur in the 2nd and 3rd century C.E. Both Mar Samuel and Rab Adda explain that the Jews used a solar calendar, but they both post-date the time of Christ by a couple hundred years. It makes sense that the Jews would use the solar calendar after their dispersion into non-Jewish cultures (after 70 C.E.). The question is whether they used it before they were dispersed. See Finegan, Jack. Handbook of Biblical Chronology: Principles of Time Reckoning in the Ancient World and Problems of Chronology in the Bible. Peabody, MA: Hendrickson, 1998. 17.
 Like Finegan, they hold that they alternated between a 29 and 30 day month, making a 354 day lunar year. The World Book Encyclopedia 1985. Chicago: World Book, 1985. 27.