“You cannot put the baby in the manger until Christmas morning, because Jesus was not born before Christmas, so it is offensive if he is in the manger before then.”
The history or start of this ritual are unknown, but it is interesting that Caitlin’s family, who she describes as being very Christian, would take offense at Baby Jesus being put in the manger before Christmas morning. She says that Joseph and Mary and the Wise Men are in the manger scene, but that Jesus is left out until Christmas morning.
What is ironic about this tradition, although I have heard of others doing this, is that Mary and Joseph should technically not be in the manger from the start either. Mary and Joseph should arrive to the manger scene on Christmas Eve, and the Wise men should not appear until after Baby Jesus. The thought for leaving Jesus out of the scene until his birth shows deference to the Bible’s portrayal of Jesus’s birth, but it also accidently ignores many of the other details surrounding his birth.