The Orthodox Church established the Synaxis of the Seventy Apostles, whom Jesus Christ appointed them and sent them out in pairs on a specific mission to the cities he would visit to preach.
Jesus Christ asked them to be constantly alert and to maintain modesty in their appearance in order to show that they had denied themselves and that they were accustomed to deprivation. The Seventy Apostles performed their mission properly and with discipline, zeal, and devotion, not only when Jesus Christ was on earth, but also after His Ascension.
Although each of the 70 Apostles is commemorated on a separate day, the Orthodox Church also commemorates them on the same day, on January 4. It is a day devoted to all who spread the Holy Gospel and contributed to the foundation of the Church in the world.
Source: Church of Cyprus