As the text does not say, commentators are left to speculate. In our minds we automatically assume the date to be a reference to the king’s reign. The difficulty with this understanding is that Nehemiah 2:1 describes an event necessarily subsequent to the events of Nehemiah 1:1–11 but dated prior to the ninth month of the twentieth year of the reign of the king (for Nisan is the first month of the year). It should also be noted that every reference to a date in the book of Nehemiah occurs with direct mention of the king (Nehemiah 2:1; Nehemiah 5:14; Nehemiah 13:6)—with this being the only exception. That leaves open the possibility that in this case the date refers not to the king but to some event important to Nehemiah himself. If that is so, the reference is likely to Nehemiah’s own years of service to the king. The implication in turn is that Nehemiah entered the service of King Artaxerxes shortly before he organized his administration as king. And that in turn speaks to the trust the king had in Nehemiah.