Church founded in the state of New York in 1830 by Joseph Smith, Jr., the basic
tenet of which is that Christ's true gospel and priesthood authority were
lost from the Earth shortly after his death, and then restored through Smith by
divine revelation and angelic messengers.
Though it is purportedly the exact same gospel and church that Christ
established during his ministry, the rather long designation is used to
distinguish the modern Church from its ancient counterpart, which was presumably
called "The Church of Jesus Christ of Saints Living in the
Meridian of Time."
Or maybe "The Church of Jesus Christ" was already taken.