Here we propose literature about the Dies Natalis of the Roman colony Iulia Augusta Numidica Simitthensium, that is Simitthus, today Chemtou, Tunisia. The Dies Natalis of the colony, founded by Augustus, was on November 27th. Moreover, we will show how literature, in particular Panegyrics, are giving us the Dies Natalis of Augusta Treverorum, today Trier. The Dies Natalis was on July 25th. This date clearly shows that there is no connection of the Dies Natalis with any supposed alignment of the decumanus, the main street of the town, with sunrise.