At the start of chapter nine Daniel is praying, inquiring about the fulfillment of Jeremiah's prophecy (Jer. 25.11-12; 29.10) that Israel's exile in Babylon would last for 49 years.
As Daniel sees it, those 49 years seem to have passed. Thus Daniel's prayer.
The answer comes from the angel Gabriel in Daniel 9.24-27 who says the exile will last not "seven weeks" of years (7 x 7 = 49 years) but "seventy weeks" of years (70 x 7 = 490 years).
In short, the exile will be much longer than expected.
Gabriel's prophecy goes on to describe how after this time the exile will end with the coming of the Messiah (the "anointed one") along with a bunch of other stuff.
Critical to the timing of this prophecy is determining when the clock is to have started on the 490 years. In Daniel 9.25 the "start date" seems to be the decree that was given to restore and rebuild Jerusalem: "So you are to know and discern that from the issuing of a decree to restore and rebuild Jerusalem..."
So when did that happen?
Opinions vary. It could have been with the decree of Cyrus (Ezra 1.1-4) which is dated around 538 BC. Or it could be the decree of Artaxeres (Ezra 7.8-26; Neh. 2.1-10) dated around 458 BC.
Many like to go with the 458 BC date because if you count the 490 years from that date you get to around 32 or 33 AD, very close to the crucifixion of Jesus.
This calculation suggests to many Christians that the seventy weeks prophecy is fulfilled by Jesus. However, as I mentioned above, there's a lot of other stuff mentioned in the seventy weeks prophecy that is confusing and/or hard to reconcile with the life and ministry of Jesus. As I've written about before, the eschatology of my faith tradition, the Churches of Christ, has been preterist. That is to say, we like to see all biblical prophecy fulfilled by the time of the destruction of Jerusalem in AD 70. What follows, then, is a preterist reading of the seventy weeks prophecy.
Here is the seventy weeks prophecy (from the New American Standard):
Daniel 9.24-27In this reading we take 9.24 to be a guiding statement, that within the span of seventy weeks (490 years) a variety of things will happen. Specifically, during this span Israel and Jerusalem will "finish the transgression." This finishing of transgression will "make an end of sin." It will also "make an atonement" that will bring about "everlasting righteousness."
 “Seventy weeks 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.  So you are to know and discern that from the issuing of a decree to restore and rebuild Jerusalem until Messiah the Prince there will be seven weeks and sixty-two weeks; it will be built again, with plaza and moat, even in times of distress.  Then after the sixty-two weeks the Messiah will be cut off and have nothing, and the people of the prince who is to come will destroy the city and the sanctuary. And its end will come with a flood; even to the end there will be war; desolations are determined.  And he will make a firm covenant with the many for one week, but in the middle of the week he will put a stop to sacrifice and grain offering; and on the wing of abominations will come one who makes desolate, even until a complete destruction, one that is decreed, is poured out on the one who makes desolate.”
In 9.26 we read that the Messiah (literally "the anointed one") will be "cut off." We also read in 9.27 that the Messiah will "make a firm covenant" and will "will put a stop to sacrifice and grain offering."
In all of this we can see a thread of interpretation that suggests that the crucifixion of Jesus is what is being referred to here. Israel will "finish the transgression" in "cutting off the Messiah." This will result in "atonement" and the dawn of "everlasting righteousness." In the ministry and death of Jesus we also see the inauguration of the new "covenant" and the end of the sacrificial system.
How does the timing of all this work out given the references to things like "sixty-two weeks" and "the middle of the week"?
Okay, 9.24 says that from "the issuing of a decree to restore and rebuild Jerusalem until Messiah" that "there will be seven weeks and sixty-two weeks." Seven weeks plus sixty-two weeks is sixty-nine weeks. That's 483 years.
If we go with the start date of 458 BC and add 483 years we get to 25 AD, the end of the sixty-ninth week. The Messiah comes, then, during the seventieth week, which goes from 26 to 33 AD. In short, the seventieth week seems to encompass the public ministry of Jesus as recounted in the gospels. And during the seventieth week the prophecy predicts that the Messiah will be killed or "cut off." And that does happen to Jesus.
We go on to take 9.27 to be a commentary about other events that are to happen during the final, seventieth week: "And he will make a firm covenant with the many for one week, but in the middle of the week he will put a stop to sacrifice and grain offering." What does it mean, then, that Jesus puts "a stop to sacrifice" in "the middle of the week"?
The "middle of the week" could refer to three and half years (given that a full week would be seven years). Thus, the middle of the seventieth week would be between 28 and 29 AD, right around the start of Jesus's ministry. You could argue that the inauguration of Jesus's public ministry with his baptism in the Jordan ended the necessity of Temple sacrifice and the start of the new covenant with Jesus's Kingdom declaration. After his baptism Jesus forgave sins directly--"the Son of Man has authority to forgive sins"--rendering the Temple obsolete. This was, we know, the most controversial aspect of Jesus's ministry, his assault upon the Temple and its sacrificial system. So maybe this is what it means that Jesus put a stop to sacrifice in the middle of the seventieth week.
All this material regarding Jesus can be made to hang together in Daniel 9 along with the historical dates.
However, the problem comes with the fact that, mixed in with these references regarding events in the life of the Messiah during the seventieth week, there are also references to the destruction of the temple in Jerusalem which happened later in AD 70:
9.26Now, Jesus uses this language of "desolation" and "abomination" (from here and elsewhere in Daniel) to prophecy about destruction of Jerusalem in his Olivet Discourse (Mark 13, Matthew 24, Luke 21). The trouble is, the destruction of Jerusalem happened in 70 AD, 37 years after the crucifixion of Jesus. This seems to push the destruction of Jerusalem past the end of the seventy weeks (which by our calculation would have ended in 33 AD).
...and the people of the prince who is to come will destroy the city and the sanctuary. And its end will come with a flood; even to the end there will be war; desolations are determined.
....and on the wing of abominations will come one who makes desolate, even until a complete destruction, one that is decreed, is poured out on the one who makes desolate.
A possible solution is to see Jesus's Olivet Discourse as an extension or addendum to Daniel's seventy weeks prophecy, in the same sort of way Daniel extended the prophecy of Jeremiah. Jesus reaches back to Daniel in the Olivet Discourse and pushes parts of the prophecy slightly forward in time, with judgment still upon "this generation."
Alternatively, in 9.24 it says that during the seventy weeks Israel will (in the NASB) "finish the transgression, to make an end of sin." An alternative reading of "to make an end of sin" is "to seal up sin." As Jesus says in a reference to the destruction of Jerusalem "all the blood" from Cain to the present would fall upon "this generation." In short, all the sins of Israel were "sealed up" and "finished" at the time of Jesus's Olivet Discourse when judgment was formally pronounced.
Seen that way, judgement upon Jerusalem comes from within the seventy weeks. That prophecy is "sealed" during the seventy weeks (9.24: "Seventy weeks have been decreed...to seal up prophecy"). That seal is then broken in 70 AD per Jesus's Olivet Discourse.
--an unpublished post, obviously, about the Seventy Weeks Prophecy. Why was it unpublished? Because after I wrote it I couldn't tell if any of it was insightful or utter rubbish. So readers be warned.