In King Benjamin's instructions to his son Mosiah2, he commanded him to make a proclamation throughout all the land that his people might be "gathered together; for on the morrow I shall proclaim unto this my people out of mine own mouth that thou art a king" (Mosiah 1:10). Chronologically and geographically speaking, a gathering of that many people in one day would be almost impossible. But John W. Welch theorizes that King Benjamin probably delivered his speech at the time of one of the three main ancient Israelite festivals when the people were already gathered together. Benjamin's speech weaves together all the major themes of the ancient New Year's holiday festival complex. The ideas that were the themes of his speech were inherent in the symbolism surrounding the festival. [John W. Welch, "King Benjamin's Speech in the Context of Ancient Israelite Festivals," 1985, F.A.R.M.S., p. 13] [For a more detailed explanation of the ancient Israelite festivals, see the commentary on Mosiah 2:1]
“I Would That Ye Should Make a Proclamation Throughout All This Land Among All This People”
In Mosiah 1 we find recorded the words which king Benjamin spoke to his son Mosiah just before the change in kingship:
My son, I would that ye should make a proclamation throughout all this land among all this people, or the people of Zarahemla, and the people of Mosiah who dwell in the land, that thereby they may be gathered together; for on the morrow I shall proclaim unto this my people out of mine own mouth that thou art a king and a ruler over this people, whom the Lord our god hath given us. (Mosiah 1:10)
According to Hugh Nibley, this kingship ceremony took place at the new year because we are told that they all brought their first-fruits (Mosiah 2:3). It was the establishment of the new government because the new king was taking over. The date was set by the old king. He said, "I'll make you king on this particular date; you send out the announcement. It's very interesting that he has his son make the announcement. why should that be? Because according to the normal order, the meeting wouldn't be held until the old king was dead. the son always announced the meeting and brought the people together because his father wasn't there anymore. If he [the king's son] would have done that before, he would be guilty of treason. He would be guilty of plotting against his father, to prematurely put him off the throne or something. So they always waited until the old king was out of the way and then his son would summon the people. Benjamin instructs his son that he is to bring the people together, to take charge of the meeting, etc. [Hugh W. Nibley, Teachings of the Book of Mormon, Semester 2, p. 10]