Sosanna’s name day is December 15, the feast of Susanna the Deaconess.
Churches that follow the Old (Julian) Calendar keep the same feast on December 28 of the civil calendar. See everything commemorated on December 15.
The saint behind the name
Susanna the Deaconess
December 15, Holy Woman, Σωσάννα η Οσιομάρτυς
The venerable martyr Susanna was the daughter of a pagan priest in Palestine who came to faith in Christ. Tradition relates that she disguised herself as a man and entered a monastery, where she was falsely accused; when her innocence was revealed she was made a deaconess at Eleutheropolis.
Also celebrating on December 15
These names share the feast, many of them other forms of the same name:
Sousanna, Susanna, Susan, Suzanne
What to say on a name day
The Greek wish is Χρόνια Πολλά (Chronia Polla), “many years.” A call or a short message on the day is what people remember. See name day wishes you can send and what a name day is.