Last year, after studying the difficulties involved in the various dates given for Daniel's 69 weeks, I concluded that the best evidence on balance favors the years 444 BC to 33 AD. And yet I've seen a lot of attempts to claim 457 BC as the beginning date. But, invariably, the 'evidence' for 457 BC is not really evidence.
One of the repeated mistakes I see from the 457 camp (I'm not always going to put "BC" when it should be understood) is confusion over the decree of Cyrus. It has to do with the building of the house of God at Jerusalem, not with Jerusalem itself. Neither Cyrus, nor Darius the Great, nor Artaxerxes in his 7th year authorized anything but the building of the Temple. But Daniel's prophecy begins with the command to rebuild the city.
Another common mistake is the ignorance of the extra-biblical archaeological record, and how it relates to the biblical record and helps support a 444 date. For example, calendars found at Elephantine (an island in the Nile) from the 5th century BC Jewish colony, help establish when Jews reckoned the 1st of Nisan. Specifically, archaeologists cross-referenced 5th century BC Egyptian and Hebrew calendars to show when (within a day) the 1st of Nisan was reckoned by the Jews in 14 instances, and in what year. Another thing learned was that the Elephantine Jews reckoned the reigning years of a king from Tishri to Tishri (the 7th month), instead of from Nisan to Nisan (the 1st month). I believe this plays a key part in reconciling what at first appears to be discrepecies in the biblical record regarding when Jehoiachin surrendered to Nebuchadnezzar, since Jeremiah reports the deportation in Nebuchadnezzar's 7th year, but II Kings 24 states that Jehoiachin came out of Jerusalem and surrendered in the king's 8th year.
More could be said, but let me hear from some others first. Which date marks the beginning of Daniel's prophecy: 457 BC or 444 BC? Or is it some other date? What does the evidence say?