Thanassis can be celebrated on 3 feasts in the Orthodox calendar. People keep the feast of the saint they were named for, or the one their family has always kept.
Every feast on which Thanassis is celebrated
| New Calendar | Feast | Old Calendar (civil date) |
|---|---|---|
| January 18 | Athanasios the Great | January 31 |
| May 2 | Athanasios of Alexandria | May 15 |
| July 5 | Athanasios of Athos | July 18 |
The saints behind the name
Athanasios the Great
January 18, Hierarch, Αθανάσιος ο Μέγας
St. Athanasios the Great, Archbishop of Alexandria, was born about the year 297 and as a young deacon accompanied his bishop to the First Ecumenical Council at Nicaea, where he stood against Arius in defense of the divinity of Christ. Made bishop of Alexandria in 328, he was driven into exile five times by Arian emperors yet never yielded, so that it was said of him: Athanasius against the world.
Name days: Athanasios, Thanassis, Thanos, Nasis, Atanas, Athanasius, Thanasis, Thanasi, Athanasis, Athanasia, Nasia, Sia

Athanasios of Alexandria
May 2, Hierarch, Αθανάσιος ο Μέγας
St. Athanasios the Great was Archbishop of Alexandria in the fourth century and the foremost defender of the divinity of Christ against the Arian heresy. Present at the First Ecumenical Council of Nicaea as a young deacon, he spent the rest of his life upholding the Nicene faith, enduring five exiles rather than yield.
Name days: Athanasios, Thanassis, Thanos, Nasis, Athanasius

Athanasios of Athos
July 5, Venerable, Αθανάσιος Αθωνίτης
St. Athanasios the Athonite was born in Trebizond in the tenth century. Drawn from a promising career in Constantinople to the monastic life, he came to Mount Athos and there founded the Great Lavra, the first of the great communal monasteries of the Holy Mountain, with the support of the Emperor Nikephoros Phokas.
Name days: Athanasios, Thanassis, Thanos, Nasis, Athanasius
Also celebrating with Thanassis
These names share the feast, many of them other forms of the same name:
Athanasios, Thanos, Nasis, Atanas, Athanasius, Thanasis, Thanasi, Athanasis, Athanasia, Nasia, Sia
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.