We read Daniel 9 starting in verse 22...
22 And he informed me, and talked with me, and said, O Daniel, I am now come forth to give thee skill and understanding.
23 At the beginning of thy supplications the commandment came forth, and I am come to shew thee; for thou art greatly beloved: therefore understand the matter, and consider the vision.
24 Seventy weeks are determined upon thy people and upon thy holy city, to finish the transgression, and to make an end of sins, and to make reconciliation for iniquity, and to bring in everlasting righteousness, and to seal up the vision and prophecy, and to anoint the most Holy.
25 Know therefore and understand, that from the going forth of the commandment to restore and to build Jerusalem unto the Messiah the Prince shall be seven weeks, and threescore and two weeks: the street shall be built again, and the wall, even in troublous times.
26 And after threescore and two weeks shall Messiah be cut off, but not for himself: and the people of the prince that shall come shall destroy the city and the sanctuary; and the end thereof shall be with a flood, and unto the end of the war desolations are determined.
27 And he shall confirm the covenant with many for one week: and in the midst of the week he shall cause the sacrifice and the oblation to cease, and for the overspreading of abominations he shall make it desolate, even until the consummation, and that determined shall be poured upon the desolate.
The Prophecy of Seventy Weeks in Daniel chapter 9, is the 490 years of uninterrupted period starting from "the time the word goes out to rebuild and restore Jerusalem," of Daniel 9:25 and ending 3½ years after Jesus' death. The starting point identified with a decree by Artaxerxes I in 458/7 BC to provide money to rebuild Jerusalem and its temple.
Now there where two earlier decrees by Cyrus and Darius’. So why don't these two decrees qualify to start the prophecy of Daniel 9:25? Well lets take a look at these two decrees. The first is the decree of Cyrus, given in his first year (537/536 B.C.) which is recorded in Ezra 1:1-4. An undated decree of Darius (520/519 B.C.) which is found in Ezra 6:1-12 merely reconfirms the decree of Cyrus. however, the first two decrees are about the temple, and its reconstruction, whereas the statement in Daniel 9:25 is concerned with the decree that resulted in the rebuilding of the city of Jerusalem.
The first two decrees can be omitted from consideration, because they deal only with the building of the temple, and not the rebuilding of the city and restoration, "that from the going forth of the commandment to restore and to build Jerusalem unto the Messiah the Prince shall be seven weeks, and threescore and two weeks: the street shall be built again, and the wall, even in troublous times." So we can see that the third decree of Artaxerxes is the one that started the prophecy of Daniel 9 and was implemented in September/October 457 B.C.
The appearance of "Messiah the Prince" at the end of the 69 weeks (483 years) is aligned with Jesus' baptism in 27 CE. The 'cutting off' of the "anointed one" is applied to the Jesus' execution 3½ years after the end of the 483 years, bringing "atonement for iniquity" and "everlasting righteousness". Jesus' death is said to 'confirm' the "covenant" between God and mankind by in 31 CE "in the midst of" the last seven years. The end of the 70th week is associated with 34 AD when the gospel was redirected from only the Jews to all peoples
Christian historicism, which is what unveils these verses from scripture, interprets prophecy as an overview of the history of the Christian church, asserting connections between historical events and statements in the Bible, and distinguishing between prophecies considered already fulfilled and those still to come. The Jews of biblical times, had taught this view in the many prophecies to be fulfilled, which were pointing to the Messiah such as those by the prophets Isaiah and Ezekiel. The early church and the precursors to the Reformation used it, Jerome in his 'Commentary on Daniel' went into the kingdoms that Daniel predicted, and we find it held by many of the Protestant Reformers and in their teachings.