Jesus and his Twelve Apostles, fresco with the Chi-Rho symbol ☧, Catacombs of Domitilla, Rome
One day after the June 29 the Feast of The Glorious and First among Apostles Peter and Paul on 30th of June according to so called new calendar in the Eastern Orthodox Church comes, the remembrace of Feast of the gathering of 12 Glorious apostles (Σύναξη των Αγίων Δώδεκα Αποστόλων).
The Secret Supper (Christ and the 12 Apostles iconographer Simon Ushakov y. 1685 (Jude the Iscariot the traitor without a halo)
"The names of the 12 Holy Apostles are: Simon (called Peter), Andrew his brother, Jacob the Zabedee and John his brother, Philip and Bartholomew, Thomas and Mathew (tax collectors), James, son of Alphaeus and Levi called (Thadeus), Simon The Canonite and Jude the Iscariot who has betrayed Christ"
(Gospel of Mathew 10:2-4)
13 When morning came, he called his disciples to him and chose twelve of them, whom he also designated apostles: 14 Simon (whom he named Peter), his brother Andrew, James, John, Philip, Bartholomew, 15 Matthew, Thomas, James son of Alphaeus, Simon who was called the Zealot, 16 Judas son of James, and Judas Iscariot, who became a traitor.
15 And in those days Peter stood up in the midst of the disciples, and said, (the number of names together were about an hundred and twenty,)
16 Men and brethren, this scripture must needs have been fulfilled, which the Holy Ghost by the mouth of David spake before concerning Judas, which was guide to them that took Jesus.
17 For he was numbered with us, and had obtained part of this ministry.
18 Now this man purchased a field with the reward of iniquity; and falling headlong, he burst asunder in the midst, and all his bowels gushed out.
19 And it was known unto all the dwellers at Jerusalem; insomuch as that field is called in their proper tongue, Aceldama, that is to say, The field of blood.
20 For it is written in the book of Psalms, Let his habitation be desolate, and let no man dwell therein: and his bishoprick let another take.
21 Wherefore of these men which have companied with us all the time that the Lord Jesus went in and out among us, (Acts 1:15-26)
The Synaxis of the Twelve Apostles. Russian, 14th century, Moscow Museum.
"Jesus had other desciples as well that were seventeen and other circles of desciples around each of the pupils, however they have alwasys been considered less venerable as they did not been so close to Christ and did not understand so well the mysterios of Christ's teaching and did not persevere as mcuh as the twelve and the seventeen of desciples. Those had been been distinguished among the King, those who have been the closest people to the Teacher" (Saint John Chrysostomos)
In Constantinople Saint King Constantine ( y. 274 – 337 ), has built a famous Church dedicated to the 12 Apostles. In historian documents there is data for a first time the feast is celebrated in the V-th century.
While the memory of each apostle has a separate day in the Church calendar yearly circle, they 12 apostles are sharing the same honor, because the Holy Scriptures and the Tradition glorifious their high efforts for building the Church on top of the corner stone that is Jesus Christ himsef and for their perseverance to accept martyrdom for Christ, thus to accent this they're is this special feast the Gathering of the 12 Glorious Apostles on 30th of June. As the Holy Scriptures says they're a friends of God (John 15:14), and when the Son of Man (Jesus) sits on the glory of his power, they all are to sit on 12 thrones, to judge the 12 Hebrew tribes (Mathew 19:28).
In first centuries the Church has been feasting all the apostles together, Later she has included saint Apostle Paul, again the full list of names of the apostles are as follows:
1. Saint Apostle Peter the First Called (commemorated 29 June and 16 of January)
2. Saint apostle Andrew the First Called – as has been called by Christ together with Peter (30 November)
3. Saint Jacob the Zebedee (30 April)
4. Saint Apostle John the Zebedee – the evangelist (26 September and 8 May)
5. Saint Apostle Philip (14 November)
6. Saint apostle Bartholomew or Nathanael (11 June and 25 August)
7. Saint apostle Thomas (6 October)
8. Saint apostle Mathew – evangelist (16 November)
9. Saint Apostle Jacob – son of Alpheus 9 October)
10. Saint Apostle Jude – fleshly brother of Christ (son of Joseph), called also Thadeus and Levi (19 June)
11. Saint Apostle Mathew (Mathias) (9 August)
12. Saint Apostle Paul (Paul of Tarsus) (29 June)
The Church books define the feast day as the "Gathering of the Twelve", because this number of 12 apostles is initial and depics Christ essence of Completeness (as he is All in everything) Mathew (10:1-5)