St. Vartan's Day is celebrated on February 19 in the Armenian Apostolic Church. It commemorates the Battle of Avarayr, fought in 451 AD, where Armenian forces, led by Vartan Mamikonian, resisted the Persian Empire's attempts to impose Zoroastrianism on Armenia. This battle is significant in Armenian history as it symbolizes the struggle for religious freedom and national identity. The day is marked by special church services, prayers, and the remembrance of the martyrs who fought for their faith. It serves as a reminder of the importance of standing up for one's beliefs and the sacrifices made for religious liberty in Armenian culture.