Inter-Hours

The Inter-Hours are brief services in the Daily Office of the Eastern Orthodox and Greek Catholic Churches. The Inter-Hours are called for during the Lenten seasons of the Church year. They are styled after the Little Hours—First Hour, Third Hour, Sixth Hour, and Ninth Hour—only briefer.
The Inter-Hours are called for during the Lesser Fasts. The structure of each Inter-Hour is as follows:

O come, let us worship...
Three Psalms
Trisagion and the Lord's Prayer
Troparia
Lord, have mercy
Concluding prayers and blessing
Prayer of St. Ephraim
Final prayer
Dismissal by the Priest

The Fixed Psalms are as follows:

Inter-Hour of the First Hour—45, 91, 92
Inter-Hour of the Third Hour—29, 31, 60
Inter-Hour of the Sixth Hour—55, 56, 69
Inter-Hour of the Ninth Hour—112, 137, 139

The Inter-Hours are only done on "days with Alleluia"; that is to say, days when the services follow a Lenten format and, as a result, the Divine Liturgy may not be celebrated. According to present-day usage, the Inter-Hours are often said only on the first day of the Lesser Fasts.