 the authors either knew or were constrained by what they might previously have supposed concerning the date of Nebuchadnezzar’s conquest of Jerusalem (which we know to have been 587 BCE) or the dating of the Persian period (which we know to have been 538-323 BCE). This was well summarized by Michael Wise:
“The year 587 [for Nebuchadnezzar] is a date modern scholars have deduced only because they have cuneiform writings to combine with the biblical clues. Ancient Jewish chronographers were less fortunate. Indeed, no one in the time of the scrolls was quite sure how long the Persian period had been … Second Temple Jews calculated the length of the Persian period using the 490 years of Dan 9:24-27. Standard practice was first to decide when those 490 years had ended or shortly would end (i.e. when Daniel’s prophecies would be fulfilled). Then one reckoned backwards from that very debatable standpoint … Since, therefore, the author of the Damascus Document cannot be presumed to have posited the year 587 BCE for Nebuchadnezzar’s siege of Jerusalem, the only proper methodology for understanding CD 1:3-11 is to turn the usual approach on its head. One must first determine when the Teacher lived, then work backwards from that point to calculate when the author believed Nebuchadnezzar was on the scene.” (Wise 2003: 63-4)
/p. 77/ In other words, the eschatologically-minded authors of the Damascus Document regarded counts which ended before their time as erroneous by definition and in need of updating or recalculation (Adler 1996 [‘updating and reinterpreting Daniel’s vision of 70 weeks persisted in Judaism up to and even after the destruction of the temple in 70’]; Collins 2010: 93-94 [‘there is no reason to believe that the 390 years of CD 1 is any more reliable as a chronological indicator than Daniel’s 490 years ... the number cannot be pressed to yield even an approximate date’]).
Instead of assuming there was a single fixed chronological system in use in ancient texts such as those found at Qumran which was adhered to generation after generation, we should think instead in terms of a ‘moving front’ for their fixing of their end-dates, with periodic recalculations and reworking of the schemes as necessary to keep the end out ahead of the present, what Cana Werman calls ‘chronographic fluidity’ (2006: 250 fn 53). The authors of Daniel had a 490-year scheme that ended in the 160s BCE. Another scheme is reflected in 4Q390/Apocryphon of Jeremiah C, written at about the same time as Daniel in the context of the Hellenistic crisis, but which foresees that crisis continuing a long time and whose authors now calculated themselves to be only in the 7th of 10 jubilees of their 490-year count. The Damascus Document sets the end of its 490-year count forty years after the death of the Teacher of Righteousness which is in the very recent past of that text’s authors. The ‘Olivet Prophecy’ and book of Revelation of the New Testament end their 490-year counts of Daniel at the time of the First Revolt in the second half of the 1st century CE (Mk 13:14; Rev. 13:1-10; 17:5). All of these are different endings of Daniel’s 490 years, a ‘rolling front’ through time for when the eschatological transformation was anticipated to happen. A chronological scheme—a 490-year count—in a text in this era might by definition have been composed recently before the time of authorship of that text, with changing ways to count the 490 as schemes were updated in light of the latest developments.
In the case of the Damascus Document, the authors, reasoning that the true numbers must give a 490-year count coming out to ahead of their own time, used 390 years which they got from Ezek. 4:4-6 to fill in the first part of the period. Then they combined that 390 with more recent numbers to make the count come out right (which must obviously end at some point ahead of when they were writing). Michael Wise is right—the 390 years of CD 1.5-8 do not inform us of when the Teacher arose, but rather how long before their time the authors determined Nebuchadnezzar had lived (a 