by Eric D. Huntsman, from his book Good Tidings of Great Joy, 6–7.
Modern revelation seems to suggest that Jesus was born on April 6 (see D&C 20:1), a proposition that has been widely supported and explained in LDS teaching since. A spring date certainly accords better with the Lucan image of shepherds abiding in the fields, but it also prompts Latter-day Saints to wonder how the current date of December 25 became standard.
Because the Gospels do not give an exact date for Jesus’ birth, together with the fact that early Christians do not seem to have celebrated Christmas, later believers were left to guess at what seemed like a probable date. Perhaps the earliest suggestion was January 6, a date associated with both the visit of the Wise Men and Jesus’ later baptism. The idea that Jesus’ “new birth” at the beginning of his ministry (Mark 1:11, when God proclaimed Jesus to be his Son after he was baptized) replaced his birth as Mary’s baby (Luke 2:7) gave some credence to this date. January 6 was also initially popular with some Christians in Egypt, where the god Osiris, who was somewhat of a Christ-type in that he died and rose again, was also honored on January 6.
However, March 25 soon became a more popular date for Jesus’ birth because it was the spring equinox in the Roman calendar. Some early Christian writers connected the beginning of spring with the creation of light and of the world, suggesting that it was a fitting day for Jesus, the True Light, to come into the world. Later, some also suggested that March 25 would be the day of his saving death at the end of his life, thus linking his coming into the world with the day when the world was redeemed. One writer, Sextus Julius Africanus (c. A.D. 160–240), connected the Roman spring equinox not with the day of Jesus’ birth but rather with the day of his conception. Significantly, placing Jesus’ conception on March 25 put Jesus’ birth nine months later on December 25, a day that was already significant because it was the winter solstice according to the original Roman calendar.
December 25 became particularly important in the third and early fourth centuries A.D., when a series of emperors—including Elagabalus, Aurelian, and eventually Constantine—made the worship of the sun a central part of Roman worship. This was because birthdays of Sol Invictus, or “the Unconquered Sun,” and another god, Mithras, both fell on the winter solstice. Later, as Christians argued that Jesus was the true source of Light and the actual “Sun of Righteousness” (see Malachi 4:2), they may have tried to displace such Roman solar deities by making it Jesus’ birthday instead. This date did not become official, however, until the Chronograph of 354, in which the church at Rome established December 25 as the date of Jesus’ birth. By the end of the century most other major churches elsewhere accepted this date as well. However, because some of the Eastern Orthodox churches continue to use the older Julian calendar, they often celebrate this date on what the more common Gregorian calendar calls January 7.
Because December 25 date fell near other Roman festivals, such as the gift-giving holiday known as Saturnalia, observing Christmas on this date allowed Christians to celebrate much like their neighbors. As Christianity spread into northern Europe, the winter date of Christmas also allowed it to gradually displace other midwinter festivals. Because of this history, commemorating the birth of Jesus on December 25 allows us to celebrate with much of the rest of the Christian world as well as enjoy a number of seasonal traditions that have accrued through the centuries.
 John Hall, “April 6,” Encyclopedia of Mormonism, 1:61–62). Jeffrey R. Chadwick, “Dating the Birth of Jesus Christ,” BYU Studies 49.4 (December 2010), 6–11, lays out the considerable variety there actually has been over the years among LDS authorities and writers in treating the dating of Christ’s birth. Though somewhat revisionist, Chadwick’s subsequent reevaluation of the issue brings much important evidence to the discussion.
 Bowler, “Dating Christmas,” Encyclopedia of Christmas, 56–57; Kelly, Origins of Christmas, 57–71; Bruce David Forbes, Christmas: A Candid History (Berkeley: University of California Press, 2007), 17–41.