Esaias’s name day is May 9, the feast of Isaiah the Prophet.
Churches that follow the Old (Julian) Calendar keep the same feast on May 22 of the civil calendar. See everything commemorated on May 9.
The saint behind the name

Isaiah the Prophet
May 9, Prophet, Ησαΐας
The Holy Prophet Isaiah prophesied in Jerusalem in the eighth century before Christ. Beholding the Lord upon His throne, with the seraphim crying Holy, Holy, Holy, he was cleansed by a burning coal and sent to call the people to repentance. His book is filled with prophecies of the Messiah, of the virgin who would conceive, and of the suffering servant wounded for our transgressions.
Also celebrating on May 9
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.