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This is the date that Joseph Smith was finally given permission to unearth the gold plates, the Urim and Thummim, and the breastplate. (JSH 1:59)
What is September 22, 1827?
"At length the time arrived for obtaining the plates, the Urim and Thummim, and the breastplate. On the twenty-second day of September, one thousand eight hundred and twenty-seven, having gone as usual at the end of another year to the place where they were deposited, the same heavenly messenger delivered them up to me with this charge: that I should be responsible for them; that if I should let them go carelessly, or through any neglect of mine, I should be cut off; but that if I would use all my endeavors to preserve them, until he, the messenger, should call for them, they should be protected."