King David
“If we keep vigil in church, David comes first, last and central. If early in the morning we want songs and hymns: first, last and central is David again. If we are occupied with the funeral solemnities of those who have fallen asleep, or if virgins sit at home and spin: David is first, last and central. O amazing wonder! Many who have made little progress in literature know the Psalter by heart. Nor is it only in cities and churches that David is famous; in the village market, in the desert, and in uninhabitable land, he excites the praise of God. In monasteries, among those holy choirs of angelic armies, David is first, last and central. In the convents of virgins, where are the communities of those who imitate Mary; in the deserts where there are men crucified to the world, who live their life in heaven with God, David is first, last and central. All other men at night are overcome by sleep. David alone is active, and gathering the servants of God into seraphic bands, he turns earth into heaven, and converts men into angels.”
— Saint John Chrysostom

The Orthodox Church uses the Greek version of the Old Testament known as the Septuagint rather than translations from the Hebrew editions. The Septuagint is the version of the Old Testament used by the Apostles when quoting the Old Testament in the New Testament. The numbering of the Psalms in the Septuagint differs from that found in Bibles translated from Hebrew:

In Orthodox Bibles: In Protestant Bibles: In Orthodox Bibles: In Protestant Bibles:
1-8 1-8 115 116:10-19
9 9 and 10 116-145 117-146
10-112 11-113 146 147:1-11
113 114 and 115 147 147:12-20
114 116:1-9 148-150 148-150

The psalter is divided into 20 kathismata, for reading at Vespers and Matins. (Kathisma means sitting, since the people normally sit during the reading of the psalms.) Each kathisma is divided into three stases (from stasis, to stand, because each stasis ends with “Glory to the Father…” at which everyone stands.)

The reading of the kathismata are arranged so that the whole Psalter is read every week. (During Great Lent, it is read twice each week). Orthodox psalters usually also contain the Biblical Odes, which are read at the canon of Matins during Great Lent. Some Orthodox psalters also contain special prayers for the departed, which are used during the wake, when the psalms are read over the body of the deceased.

The schedule for reading the Psalms each week
Weekday Kathismata at Matins Kathismata at Vespers
Sunday 2, 3 None
Monday 4, 5 6
Tuesday 7, 8 9
Wednesday 10, 11 12
Thursday 13, 14 15
Friday 16, 17 18
Saturday 16, 17 1

 

The schedule during Great Lent
Day Matins 1st Hour 3rd Hour 6th Hour 9th Hour Vespers
Sunday 2, 3
Monday 4, 5, 6 7 8 9 18
Tuesday 10, 11, 12 XIII 14 15 16 18
Wednesday 19, 20, 1 II 3 4 5
Thursday 6, 7, 8 IX 10 11 12 18
Friday 13, 14, 15 19 20 18
Saturday 16, 17 1