It was told that the Roman Colonia Marciana Ulpia Traiana Thamugadi (Timgad in Algeria), founded in 100 AD, had been oriented to the sunrise on the day of Trajan’s birthday, given as September 18. This Gregorian date corresponds to September 17 of the Julian Calendar. Here we use software such as CalSKY and Stellarium to investigate the sunrise azimuth and compare it to the direction of the decumanus of the Roman town. After the archaeoastronomical analysis we can conclude that the assertion concerning the orientation of Timgad to the sunrise of the day of Trajan’s birthday could be true.
