Recurrence pattern: every year on November 29.

The Feast Day of Thaddeus and Bartholomew the Apostles is observed in Armenia and by the Armenian diaspora, taking place every year on November 29. This day honors Thaddeus and Bartholomew, who are venerated as patron saints of the Armenian Apostolic Church. According to tradition, Thaddeus was the first to bring Christianity to Armenia, curing King Abgar V of leprosy, which led to the king's conversion. Bartholomew later came to Armenia to continue this mission and is believed to have been martyred for converting the king to Christianity. The biggest celebrations occur at Etchmiadzin Cathedral in Vagharshapat, the mother church of the Armenian Apostolic Church. This feast day reflects the historical significance of these apostles in establishing Christianity in Armenia, although Saint Gregory the Illuminator is credited with making Armenia the first nation to adopt Christianity as its official religion.