Dies natalis (“birth day”) was in the Roman world the day of birth or the anniversary of the construction or event. Ancient Romans celebrated their birthday every year, in contrast to the Greeks who celebrated their birth on the same day each month of the so-called libation – drinking the most often mixed with water wine.
The custom dies natalis derived from the Roman custom of remembering the deaths of close relatives (anniversarium), taken over by Christians to whom they gave a different meaning and character.
Roman dies natalis was related to the cult of Genius or Juno (women). Usually important politicians paid attention to their birthdays and properly arranged public events to overlap. For example, Pompey the Great has been waiting seven months to return from her campaign in the East and be able to triumph on his birthday. In ancient Rome, the time of birth was also the moment of remembering the deceased.
Dies natalis also referred to the creation of the temple or its thorough renovation. At that time, this day was considered the “birth” of the deity and celebrated accordingly. Rome’s birthday was in turn celebrated on April 21, in the so-called Parilia – festival in honor of Pales – the goddess of shepherds and their herds.
The birthday of the emperors naturally had a public ceremony. Very often the day of emperor’s birth was associated with dies natalis of temple of some deity. And so the day of September 23 was the birth date of Augustus, which also became the birthday of the Temple of Apollo on Field of Mars. Birthdays were called natalicium.