According to the IDF..

The mosaic is from the 3rd or 4th century, many years before the official recognition of Christianity.
There is also a mentioning of Jesus as a God, the lack of a Cross, and the fish in the mosaic- all point to a very early era of Christianity.
Megiddo prison Church (A.K.A Armageddon Church)- the 3rd century Church excavated in Megiddo prison.