Many of the themes that show up in 2 Nephi 6–10 have been identified as typical of the New Year and the Feast of Tabernacles on the regular Jewish calendar. At that time, ancient Israelites also typically held coronations and the renewal or re-enthronement of the king. Every year there was a renewal of the people’s loyalty to obey the king of Israel. So, what we have here in Jacob’s speech is likely a covenant renewal speech. We know that this is dealing with covenant because 2 Nephi 9:1 states Jacob’s purpose as follows: "Behold, my beloved brethren, I have read these things that ye may know concerning the covenants of the Lord that he has covenanted with all the House of Israel." Several parts of Jacob’s speech follow old traditions that the Nephites carried on.
For example, several scholars, both those who are and are not Latter-day Saints, have identified in the Old Testament a covenant treaty pattern. This pattern was not just limited to the Hebrews. Such "treaty-covenants" had (1) a preamble, (2) gave a historical overview, (3) stated stipulations of the covenant, (4) extended blessings and curses structured as "if you do this, this will happen; if you do not do it, such and such will happen." Then there was (5) a witness formula, and (6) a recording of the covenant.
Joshua 24 offers an example of an ancient covenant renewal: "Choose ye this day whom ye will serve; whether the Gods which our fathers served that were on the other side of the flood, or the gods of the Amorites, in whose land ye dwell, but as for me and my house, we will serve the Lord." Jacob’s words in 2 Nephi 6–10 can be read well in the context of that treaty-covenant pattern, as covenants were renewed on several different occasions, including coronations and covenant-renewal festivals. Such is quite prominently the case at the coronation of Mosiah by his father Benjamin.
One might get the impression that this was Nephi’s inauguration or coronation as king. However, 2 Nephi 5:28 tells how the Nephites built a temple, and thirty years passed away, and then Nephi made the record, and then another ten years had passed away (5:34). So, Jacob’s speech appears to have been given at least ten years after Nephi’s coronation. It may have been a ten-year anniversary celebration.
Book of Mormon Central, "Did Jacob Refer to Ancient Israelite Autumn Festivals? (2 Nephi 6:4)," KnoWhy 32 (February 12, 2016).