Most people named Yannis keep their name day on January 7, the feast of John the Baptist. The Orthodox calendar has 2 other feasts for the name.
Every feast on which Yannis is celebrated
| New Calendar | Feast | Old Calendar (civil date) |
|---|---|---|
| January 7 | John the Baptist | January 20 |
| May 8 | John the Theologian | May 21 |
| June 24 | Nativity of John the Baptist | July 7 |
The saints behind the name

John the Baptist
January 7, Great Feast, Ιωάννης ο Πρόδρομος
On the day after Theophany, the Church gathers to honor St. John the Forerunner and Baptist, the greatest of the prophets, who was found worthy to baptize the Lord in the Jordan. Son of the priest Zacharias and the righteous Elizabeth, John lived in the wilderness in fasting and prayer, preaching repentance and preparing the way of the Lord.
Name days: Ioannis, Giannis, Yiannis, Yannis, Yanni, Giovanni, John, Jean, Juan, Ivan, Vanya, Yianni, Gianni, Giannakis, Prodromos, Johnny, Ioanna, Gianna, Yianna, Giannoula, Joanna, Joanne, Joan

John the Theologian
May 8, Apostle, Ιωάννης ο Θεολόγος
St. John the Theologian, the Beloved Disciple, was the son of Zebedee and brother of James, called from his nets by the Lord. He leaned on the breast of Christ at the Mystical Supper, stood by the Cross when the others had fled, and received the Theotokos into his care. He wrote the Fourth Gospel, three Epistles, and the Revelation.

Nativity of John the Baptist
June 24, Great Feast, Γέννηση Ιωάννου Προδρόμου
The Nativity of St. John the Forerunner is celebrated on June 24, six months before the Nativity of Christ. The Gospel of Luke recounts how the Archangel Gabriel announced to the aged priest Zacharias that his barren wife Elizabeth would bear a son; struck mute for his doubt, Zacharias regained his speech at the naming of the child and prophesied that the boy would be called the prophet of the Most High.
Also celebrating on January 7
These names share the feast, many of them other forms of the same name:
Ioannis, Giannis, Yiannis, Yanni, Giovanni, John, Jean, Juan, Ivan, Vanya, Yianni, Gianni, Giannakis, Prodromos, Johnny, Ioanna, Gianna, Yianna, Giannoula, Joanna, Joanne, Joan
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.