According to John Lefgren, the astronomical full moon was visible over America during the night preceding the birth of Christ (April 6, 1 B.C.) The Book of Mormon states that there were to be "great lights in heaven" (Helaman 14:3) but does not indicate the nature or source of the light.
Isaiah 30:26 says that "the light of the moon shall be as the light of the sun." Jewish tradition has considered these words to be related to the advent of the Messiah. Solomon ben Isaac Rashi, a leading Jewish commentator on the Bible and Talmud in the eleventh century, stated that in the time of the Messiah "there will be in the world only the brilliance of splendour and the sight of the Holy Spirit. In the days of the Messiah the light of the moon shall be as the light of the sun. Astronomical calculations indicate that the night before Christ's birth was a night of a full moon, and the Book of Mormon relates that at the setting of the sun in normal course there was yet "no darkness in all that night, but it was as light as though it was mid-day" (3 Nephi 1:19). Does this not partially fulfill the Messianic expectations of the Jews? [John C. Lefgren, April Sixth, p. 32]
“There Was No Darkness in All That Night but It Was as Light as Though It Was Mid–day”
According to Ammon O'Brien, the Nephite record is clear in stating "there was no darkness in all that night, but it was as light as though it was mid-day" (3 Nephi 1:19; see also Helaman 14:3). Observing this detail, we may therefore ask, What was the source of that light? Was it the sun? Not according to the Mormon account which in the prophecy of Samuel the Lamanite, declares that the sun would continue on its course as normal: "for ye shall know of the rising of the sun and also of its setting" (Helaman 14:4). This is confirmed in 3 Nephi 1:15 which states, "for behold, at the going down of the sun there was no darkness."
So again we ask, What was the cause or source of this light? A plausible answer to this appears in native American Indian legends. The Great Star, which in the Book of Mormon is called the New Star, was apparently the orb of light which banished the darkness from the legendary night of which we speak.
Bearing in mind the moon's role in all of this, we may observe that while the legends indicate the moon was excessively brilliant on this occasion, it is most probable that the moon itself was actually going about its normal course, just as the sun had gone down over the horizon as normal. My [O'Brien's] hypothesis, is that there was no geo-thermal nor cosmic activity within the moon itself, but its excessive temporary brightness was due entirely to the reflection of the intense light emitted by the "New Star." Thus as the Great Star illuminated the sky, the moon was immersed in that light, and by virtue of its reflective nature which is demonstrated every time we see it shining brightly in the sky off borrowed light, the moon became extremely brilliant in white light for the duration of the effect.
One prolific source of information on the ancient culture of Mexico is the work of Fray Bernadino de Sahagun. Looking at Book 7 Chapter 2 in his Historia General de las Cosas de Nueva Espana (Florentine Codex) which deals with the cosmology of the Nahuas, we find the legend of a night when the moon appeared in glory. The following words are recorded: "Like the sun he shone, and it was like daytime. It was said, 'It is almost like day; everywhere it is bright. Light is spread everywhere.'" [Ammon O'Brien, Seeing beyond Today with Ancient America, pp. 271, 263-264]
3 Nephi 1:19 There was no darkness in all that night, but it was as light as though it was mid-day: The picture [[Illustrated]] which has developed thus far [from ancient native American Indian legends] indicates that a total of three brilliant orbs were involved in the spectacle. (1) The New Star, or Nanahuatzin which shone "as the sun." (2) The moon which for a time attained "equal brightness" to that of Nanahuatzin. (3) Thirdly, we have the actual sun which also had an integral role in this.
In normal circumstances, we see that sometimes the moon is still visible in the sky even after the morning sun has come up over the horizon. Imagine then the wondrous sight it would have been at the time when the New Star emerged and shared the sky with the moon, if at dawn the sun began to rise over the horizon while the other two orbs with all their light were still visible in the sky. I [Ammon O'Brien] raise this postulation because of a very peculiar statement in the archaic Quiche manuscript of Don Juan de Torres, grandson of the last Quiche King. It is said that in the ancient time, a certain three fold division of the ancestral kingdom was initiated "in a day when three suns were visible at the same time." [Ammon O'Brien, Seeing beyond Today with Ancient America, p. 271]