I have recently been studying this prophecy at some length.
I believe that Daniel's "70 Weeks" began to run when Nehemiah ordered the work to begin on the rebuilding of Jerusalem's wall after Artaxerxes issued a decree in his 20th year which permitted Nehemiah to return to Jerusalem to rebuild that Holy City. (Neh. 2)
Some see a problem with this understanding. For Daniel's "Seventy Weeks" are widely understood to refer to a period of 490 years, and all historians now assure us that Artaxerxes' 20th year of ruling Persia took place in 445 BC. And 490 years after 445 BC brings us to 46 AD, which was quite a few years after the death of Christ.
How then can I understand that Artaxerxes' decree in his 20th year as king has anything to do with Daniel's "Seventy Weeks" prophecy? Because I am convinced that Nehemiah did not return to Jerusalem and give his command to begin rebuilding that city until the year 440 BC, even though the Bible tells us that Nehemiah had been granted permission by Artaxerxes to issue such a command in Artaxerxes' 20th year as king of Persia, which historians assure us took place in 445 BC. (Neh. 1:1-6)
I believe this because the first century Jewish historian, Josephus, tells us that Nehemiah "came to Jerusalem" not "in the twentieth year of Artaxerxes" as the Bible seems to say, but in his "twenty and fifth year." (Ant. XI, 5, 7) The fact is that the Bible does not actually say that Nehemiah returned to Jerusalem in Artaxerxes' 20th year. It only tells us that Artaxerxes then gave Nehemiah permission to do so. While Josephus, on the other hand, tells us of the time that Nehemiah actually "came to Jerusalem." (It is also possible that Nehemiah reckoned the reign of Artaxerxes in a substantially different manner than historians do today and Josephus did in his day. I'll explain this later.)
Concerning this matter, in his book, "History Of Israel" (third edition, 1981, pg. 381) John Bright tells us, "The Bible gives us the impression that Nehemiah set out at once, accompanied by a military escort (Neh.2:9). But Josephus (Ant. XI, 5, 7), who follows the Septuagint text, the first part of which is preserved in 1 Esdres, places his arrival only in 440. Though assurance is impossible, this may be correct. If Nehemiah first went to Babylon and collected Jews to accompany him, as Josephus has it, and then having presented his credentials to the satrap of Abah-nahara, attended to the procurement of building materials before proceeding to Jerusalem, as he possibly did since work was begun soon after his arrival, the date is not unreasonable."
Some who harmonize the accounts of Nehemiah and Josephus in this way point out that it took Solomon nearly four years to procure similar kinds of building materials before he was able to begin building the Temple. (2 Chr. chapters 1 and 2 and chapter 3, verses 1 and 2) And Solomon was much better funded than Nehemiah, and unlike Nehemiah, Solomon was able to conscript all the labor he needed for his building project, rather than having to spend time finding volunteers.
Other scholars agree with Bright's assessment of Josephus' probable accuracy in this matter. For instance, Sigmund Mowinckel, a highly regarded Scandinavian Bible scholar, believes that Josephus used a separate Greek version of Nehemiah that in several respects differed from that preserved in the LXX. He argues that Josephus' chronological information on the Persian kings did not result from his own calculations, or from any mistakes some say he must have made in this matter. Mowinckel argues that Josephus must have been quoting from a now lost Greek version of Nehemiah. On Josephus' statement about the 25th year of Artaxerxes, Mowinckel maintains that Josephus' figures are most likely the original ones. He writes, "In my opinion the balance [of evidence] is in favor of [the figure] '25'." (Vol. 3, p.45 of Studien zu dem Buche Ezra-Nehema, Vols. 1-3, Oslo, 1964)
But how does the fact that Nehemiah did not give his order to begin rebuilding Jerusalem until 440 BC help us to make sense of Daniel's "Seventy Weeks" prophecy? As most students of Bible prophecy know, Daniel's "seventy weeks" are generally understood as referring to seventy weeks of years (seventy sets of seven years) totaling a period of 490 solar years. But the Jews used a lunar calendar! Their years were lunar years, not solar years. So a week of years to the Jews would have meant seven lunar years. And seventy weeks of years to the Jews would have meant 490 lunar years, not 490 solar years.
At the time of Daniel, on average about every three years, the Jews added an extra month to the end of their lunar calendars to make sure that they never fell too far out of sync with the solar year. But at the time Daniel wrote his "Seventy Weeks" prophecy the Jews had no set system of doing so. When they decided that it was time to add an extra month to their calendars they called this extra month "second Adar." However, the fact that they then sometimes added an "intercalary" month to their lunar calendars does not change the fact that, to the Jews, a "year" normally meant 354 days. For that is the number of days which one of their calendars most often contained. Their calendars usually consisted of six 29 day months and six 30 day months. So, to the Jews who lived at the time Daniel wrote his "Seventy Weeks" prophecy, a “year” would have been understood to mean a lunar year, and a "week" of years (literally a “seven” of years) would have been understood to mean seven lunar years. And “seventy weeks” of years would have been understood to mean 490 lunar years, none of which were then either automatically or routinely solar-adjusted.
Now, since one lunar year contains 354.367 days, 490 lunar years contain 173,639.83 days. And 173,639.83 days divided by 365.2425 (the number of days in a solar year) equal 475.40 solar years. With these things in mind, I have come to conclusion that Daniel's "seventy weeks" were a period of 475.4 years which ran from 440 BC to 36 AD. I believe those 475.4 years began at the time Nehemiah gave his "commandment to restore and to build Jerusalem" (Dan. 9:25 KJV; Neh. 2:17,18). And I believe those 475.4 years ended at the time God acted to "confirm the [new] covenant with many" by pouring His Holy Spirit out on Gentiles for the first time (Dan. 9:27 KJV; Acts 10). I believe the "many" here referred to were the "many nations" God promised Abraham that he would one day become the father of. (Gen. 17:4)
As anyone who has thoroughly studied the history of this prophecy's interpretation knows, this is by no means a new idea or a novel one. In the year 221 AD Julius Africanus in his work entitled "Chronographia" argued that the 490 years were lunar years of 354 days each, which he converted into 475 solar years. He counted them from the 20th year of Artaxerxes, which he correctly dated to the 4th year of the 83rd Olympiad (=445/444 BC). From this date, he said, to "the 16th year of the reign of Tiberius Caesar (30/31 AD, his date for the death of Christ), there are reckoned 475 years, which take 490 according to the Hebrew numeration, as they measure the years by the course of the moon; so that, as is easy to show, their year consists of 354 days, while the solar year has 365 1/4 days." (Africanus' Chronographia XVI, 3 translated in The Ante-Nicence fathers, Vol. VI ed. A. Roberts & J. Donaldson, p. 135) Many later expositors followed Africanus in doing this.
I believe that the facts of history, together with a knowledge that the Jews used a lunar calendar, combine to show that the Messiah (meaning "anointed one") was first presented to Israel in the year 29 AD by John the baptist, after sixty-nine weeks of lunar years had passed, when John anointed Jesus of Nazareth with the waters of his baptism in "the 15th year of Tiberius Caesar." (Luke 3:1,21). At that time Jesus Christ was "cut off" from his people and, quite literally, "had nothing for himself." (Dan. 9:26) For he then began a forty day long fast in the wilderness. Then, after three and a half years, in the middle of Daniel's seventieth week, in the spring of 33 AD, Christ's sacrificial death brought an end to the Jewish system of sacrificial offerings. (Dan. 9:27) Finally, three and a half years later, at the end of Daniel's "Seventy Weeks," in the early fall of 36 AD, Christ "confirmed a covenant with many" (Dan. 9:27) when he, for the first time, poured out his Holy Spirit on non-Jewish people. (Acts 10)
Doing so confirmed the fact that God, from that time forward, would give everyone who put their faith in Jesus Christ, both Jews and Gentiles, complete forgiveness of their sins and eternal life. With this fact in mind, the good news of what Jesus Christ had done for mankind then began to be preached to all people on earth, just as Christ said that it would be. (Math. 24:14)
There is another solution to this ancient puzzle that also fits all the facts of history. This solution eliminates the problem of Nehemiah taking five years to get to Jerusalem, which some people have a hard time accepting. Historians tell us that Artaxerxes did not gain legal control of Persia's throne until six years after the assassination of his father Xerxes. Because he did not, it is very possible that Nehemiah did not count the first six years of Artaxerxes' reign during which its legality was being contested. Those who have thoroughly studied the way in which Bible writers reckoned the reigns of Israel's and Judah's kings tell us that at times they apparently employed this "legal count" system of reckoning.
If this is true, then when Nehemiah referred to Artaxerxes' 20th year he would have been referring to the same year Josephus referred to when he told us Nehemiah came to Jerusalem in Artaxerxes' 25th year, 440 BC.
The historical information which strongly suggests that Nehemiah very likely employed this "legal count" system of reckoning is contained in the works of several ancient historians. I'll here give you a condensed version of it.
Artaxerxes came to the throne of Persia in August of 465 BC following the murder of his father Xerxes. To gain the throne for himself Artaxerxes and his supporters, the real murderers, blamed Xerxes' murder on the rightful heir to the throne, Artaxerxes' older brother crown prince Darius. They then had Darius unjustly executed. For the next six years Artaxerxes' legal right to rule Persia was hotly disputed. Why? Because ancient Persia was not a "banana republic" in which anyone willing to assassinate their country's head of state and then take his place with the support of several armed friends had just as much a legal right to run their country's government as anyone else did. Ancient Persia was then governed by a hereditary monarchy. In that monarchy, upon the death of a king, the right to rule legally passed from a father to his first born son. If that first born son was, for some reason, legally disqualified from becoming king, the right to rule then passed to the king's next oldest son. If a king had no son who was legally qualified to inherit the throne, upon his death the right to rule passed to his oldest brother.
Following king Xerxes' murder and the execution of crown prince Darius, Artaxerxes' older brother Hyspases was legally next in line to inherit Persia's throne. However, Hyspases was then away governing the Persian Provence of Bactria. Because he was, Artaxerxes was able to sit on his father's throne. It is said that for the next few years Hyspases rightly maintained that he held the legal right to rule Persia. Sometime during the first few years of Artaerxes' legally disputed reign as king, he and his older brother Hyspases met on the field of battle to resolve this issue, and some others. In Artaxerxes' effort to suppress what historians call "the Bactrian revolt," he then killed his older brother Hyspases. However, when Artaxerxes killed Hyspases he did nothing to remove the cloud of illegitimacy that then hung over his rulership of Persia. If anything, he only darkened that cloud. For a son or a brother of a king who killed the king was not legally allowed to inherit the kingdom from the king he had killed. So, at the time Artaxerxes killed Hyspases, the right to rule Persia legally passed to Xerxes full brother, Achamenes, who was then away governing Egypt.
It was not until the year 459 BC that Artaxerxes finally gained the legal right to rule the Persian empire, an empire he had been illegitimately ruling since 465 BC. For it was in that year that Artaxerxes' uncle Achamenes was killed in a battle in Egypt. It was only at that time, in 459 BC, that Artaxerxes was finally able to legally wear the crown of the king of Persia.
Nehemiah serving at the King's court would have been aware of these legal matters which put the legality of the first six years of Artaxerxes' reign in question. If Nehemiah, like other Bible writers who recorded chronological information, did not count years of a king's rule in which their right to rule was legally in question, he would have counted 459 BC as Artaxerxes' first year as Persia's king. And if Nehemiah counted 459 BC as Artaxerxes' first year, he would have counted 440 as Artaxerxes' 20th year.
In other words, we have strong reason to believe that Nehemiah may have reckoned the reign of Artaxerxes differently than the way in which it was then commonly reckoned, the way in which Josephus' sources reckoned it, and the way in which it is commonly reckoned today. When Nehemiah wrote of Artaxerxes' "20th year" he may not have been referring to the year 445 BC, as has long been thought, but to 440 BC, just as Josephus clearly was when he told us that Nehemiah came to Jerusalem in Artaxerxes' "25th year."
And sixty-nine "sevens" of years (483 lunar years) after 440 brings us to AD 29, the year Jesus became the Messiah.
My verse by verse commentary of Dan. 9:24-27 (NAS) is [in brackets.]
24 "Seventy weeks [490 lunar years] have been decreed for your people and your holy city, to finish the transgression, to make an end of sin, to make atonement for iniquity, to bring in everlasting righteousness, to seal up vision and prophecy and to anoint the most holy place.
25 "So you are to know and discern that from the issuing of a decree ["from the going forth of the commandment" - KJV] to restore and rebuild Jerusalem [Nehemiah's on site order to begin rebuilding Jerusalem's wall, upon his return to Jerusalem in Artaxerxes' 25th year, as per Josephus, which historians identify for us as 440 BC] until Messiah the Prince [Jesus Christ] there will be seven weeks and sixty-two weeks [7 x 7 lunar years + 62 x 7 lunar years = 483 lunar years. 483 lunar years from 440 BC = 29 AD, which was "the fifteenth year of Tiberius Caesar," in which year Jesus was baptized]; it will be built again, with plaza and moat, even in times of distress. [The first "seven weeks" - 49 lunar years - ran from July of 440 BC until January of 392 BC, during which time the city of Jerusalem was completely rebuilt, despite great opposition from neighboring nations.]
26 "Then after the sixty-two weeks the Messiah will be cut off and have nothing [Following Christ's baptism he cut himself off from all human contact while he literally "had nothing," as he then fasted in the wilderness for forty days.], and the people [Rome's armies] of the prince who is to come [General Titus, the son of the Roman Emperor Vespasian, thus a "prince"] will destroy the city and the sanctuary [Rome's destruction of Jerusalem and her Temple in 70 AD]. And its end will come with a flood [the hoards of soldiers who then descended upon the city]; even to the end there will be war; desolations are determined. [All of the words in verse 26, following its reference to "the Messiah" being cut off and having nothing, should be read parenthetically. For they refer to events which would occur 30 - 34 years after the "seventy weeks" came to an end.]
27 "And he [the Messiah] will make a firm covenant with the many ["confirm a covenant" - NIV - referring to the "New Covenant" which was established by the death of Christ and confirmed with "many" by the outpouring of the Holy Spirit on the gentiles, as recorded in Acts chapter 10. Romans 15:8-12 tells us that the covenant promises which Christ "confirmed" were those God made to the patriarchs concerning the Gentiles. The "many" here referred to are all the nations of the earth, Jews and Gentiles. God told Abraham, in Gen. 17:4, that he would become the father of "many nations."] for [The word "for" here is absent from the Hebrew. I believe the context strongly suggests that the word "after" should instead be here inserted.] one week [at the end of the 70th "week" which ended in 36 AD], but in the middle of the week [again the 70th "week," the middle of which was the spring of 33 AD] he [the Messiah] will put a stop to sacrifice and grain offering [which Jesus Christ's sacrificial death brought an end to]; and on the wing of abominations will come one who makes desolate [In Mark 13:14 and its parallel passage, Luke 21:20, Jesus himself clearly identified the "abomination of desolation spoken of by Daniel the prophet" as the "armies" which he said would "surround Jerusalem" prior to its destruction in 70 AD.], even until a complete destruction, one that is decreed, is poured out on the one who makes desolate." [Jerusalem's desolator, General Titus, became Emperor of Rome in 79 AD. Within months Mount Vesuvius erupted burying Pompeii. The following year, 80 AD, a fire destroyed much of Rome. Titus uttering "the fire has ruined me" was forced to sell or strip all of his imperial estates to hasten Rome's recovery. Then, in the fire's wake, one of the worst plagues on record descended upon Italy. Finally, on September 1, 81 AD, for reasons unknown, Titus fell painfully ill and died, only two years after gaining Rome's throne.]