Possibly 8th century
Church of San Giovanni Eleemosynario, Venice, Italy
The Virgin Mary is barely noticeable behind the child in the manger, but otherwise the relief covers all the main elements in a traditional Nativity: The pensive Joseph (bottom left), the shepherds on the right and magi on the left, the midwives washing the child (bottom center), and the manger, where the beasts appear to feed on the child.
My source for the date is the diary of a traveler who visited the church and asked an employee there about the relief.
This image in full resolution
Detail of the manger
More of the Nativity
Photographed at the church by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.