Arsenia’s name day is May 8, the feast of Arsenios the Great.
Churches that follow the Old (Julian) Calendar keep the same feast on May 21 of the civil calendar. See everything commemorated on May 8.
The saint behind the name
Arsenios the Great
May 8, Venerable, Αρσένιος ο Μέγας
Arsenios was a learned Roman deacon chosen by the Emperor Theodosius as tutor to his sons Arcadius and Honorius. Praying for guidance, he heard a voice telling him to flee from men and be saved, and he departed secretly for the desert of Scetis in Egypt.
Also celebrating on May 8
These names share the feast, many of them other forms of the same name:
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.