On which day does the naming ceremony take place?

The naming ceremony in ancient Roman culture, known as the "dies lustricus," was a significant event in which a newborn child was formally given their name and welcomed into the family and society. This ceremony typically occurred on the eighth day after birth for boys and the ninth day for girls, serving as an important rite of passage. During this occasion, various rituals were performed, which often included purification rites and the announcement of the child's name.

The other options do not pertain to the specific naming ceremony. For instance, "dies natalis" refers to the day of an individual's birth or birthday, while "dies faculis" is not a recognized term in Roman culture. "Dies paterna," though hints at something paternal, does not specifically connect to the naming process. These distinctions clarify why the "dies lustricus" is the correct choice regarding the timing of the naming ceremony.