“The Nephites adjusted their calendar so as to begin a new dating era with the birth of Jesus; and according to their chronology, the storms and the darkness and the crucifixion came to pass on the fourth day of the first month of the thirty-fourth year. (3 Ne. 8.) Then ‘in the ending’ of that year (3 Ne. 10:18–19), several months after the Ascension on Olivet, Jesus ministered personally among the Nephites for many hours on many days” (McConkie, Mortal Messiah, 4:306–7).
The superscription to 3 Nephi 11 was part of the ancient record translated by the Prophet Joseph Smith and dictated by him to his scribe, except for the phrase “comprising chapters 11 through 26” (see also, for example, 2 Nephi, Mosiah 9, and 4 Nephi).