Diomidis’s name day is August 16, the feast of Diomedes the Physician.
Churches that follow the Old (Julian) Calendar keep the same feast on August 29 of the civil calendar. See everything commemorated on August 16.
The saint behind the name
Diomedes the Physician
August 16, Martyr, Διομήδης
Saint Diomedes was a physician from Tarsus in Cilicia who healed both bodies and souls, bringing many to Christ. He settled in Nicaea, where he was arrested under Diocletian and died on the way to trial.
Also celebrating on August 16
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.