Thursdays in the Orthodox Church are devoted to the Holy Apostles and the Great Hierarchs, especially St. Nicholas of Myra, the Wonderworker. As someone noted earlier, Thursday is the “twelfth” day of the week (if Sunday is eight) thus the association of the 12 Apostles – though which came first – the designation or the reckoning is known only to the angels – but that was Monday…
St. Paul states: the Church is built upon the foundation of the Apostles and the Prophets, Jesus Christ Himself being the chief cornerstone” (Eph. 2:20). The “prophets” here refer to the Old Tesament writers. But for the present the Church stands as well on the living work of the Apostles, and I might add that great number of saints who bear the title “equal-to-the-apostles” not because they held such a rank in the Church, but their actions of proclaiming Christ was either equal to the Apostles in its importance (as Mary Magdalene, Equal to the Apostles, is as the first witness of the resurrection), or because their work brought about the conversion of whole nations (St. Vladimir, St. Patrick, St. Nina of Georgia, etc.).
Nothing replaces the cornerstone, for it is always Christ that is preached. But it is significant that what St. Paul cites as the foundation of our life and existence in Christ are people. It is the living stones of the Apostles that make our faith possible. And those foundations continue with the living apostolic witness of the Church. For we have not accepted mere theory about the risen Lord, or a mere set of abstract doctrinal statements, but the Living Lord Himself, who is presented to us in the Apostolic witness. I know Christ – the same Christ as was known and preached. Thus the Church remains a living Church, not because of historical witness, but because that “historical” witness abides in the Church in a living form, whether in the living successors of the Apostolic work, the Bishops, or in those who, gifted by God, continue that same living witness, all, of course, through the abiding, living presence of the Spirit.
As for St. Nicholas, great wonderworker and Ecumenical Teacher! Why are some saints so popular in the Orthodox Church? I assure you it is not their historic importance. St. Nicholas was but a minor voice and bishop at the council of Nicaea. It is the fact that as an intercessor before God on behalf of the people of God, he remains powerful and dependable. People love St. Nicholas because they know him! and they know the power of his prayers! All the historical arguments by all the theologians cannot change this simple existential vote of the people of God. Thus St. Seraphim, St. Nektarios of Aegina, St. Panteleimon, and a host of others who are not large forces in the pages of anyone’s history book, remain among the most active members of every congregation. I cannot explain one saint over another – but I know the power of their popularity and have watched it grow even within the ranks of converts. Go figure.