Antipas’s name day is April 11, the feast of Antipas of Pergamon.
Churches that follow the Old (Julian) Calendar keep the same feast on April 24 of the civil calendar. See everything commemorated on April 11.
The saint behind the name

Antipas of Pergamon
April 11, Martyr, Αντίπας
St. Antipas was Bishop of Pergamon in Asia Minor in the first century, a disciple of the Apostle John. He is named in the Book of Revelation, where the Lord Himself calls him my faithful witness, slain among you where Satan dwells. Tradition relates that he was put to death by the pagans of Pergamon for refusing to honor their idols.
Also celebrating on April 11
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.