I have heard somewhere along the way that Jesus Christ’s birthday is April 6th, which is the Mormon Church’s birthday. Do we know this for certain? How? From where? Thanks so much.
The answer to your question is found in D&C 20:1,
The rise of the Church of Christ in these last days, being one thousand eight hundred and thirty years since the coming of our Lord and Savior Jesus Christ in the flesh, it being regularly organized and established agreeable to the laws of our country, by the will and commandments of God, in the fourth month, and on the sixth day of the month which is called April-
President Joseph F. Smith made the following illuminating comments on that verse, as quoted by President Joseph Fielding Smith,
“Strictly speaking, if this Church was organized one thousand eight hundred and thirty years since the coming of our Lord and Savior in the flesh, then the sixth of April must have been the anniversary of the Savior’s birthday. If the organization of the Church had been before or subsequent to that date, if only by one or any number of days, the great event would have been more or less than one thousand eight hundred and thirty years, by just so many days (This argument also holds good as to the year of Christ’s birth). Opinions formed by the study of chronological events may or may not be accurate. But we would scarcely think the Lord would make any mistake about dates. Least of all he who was born on that day, and on that day thirty-three years later was crucified.” (Quoted by B. H. Roberts in the “Outlines of Ecclesiastical History” p. 17.) (Joseph Fielding Smith, Church History and Modern Revelation, Vol 1, pp 85 – 86)