Ascension of our Lord

From the day of the Ascension of the Lord till leavetaking, "O Heavenly King..." is substituted by the Ascension troparion.
Ascension of the Lord, Troparion, Tone IV —

Thou didst ascend into glory, O Christ our God, having gladdened Thy disciples by the promise of the Holy Spirit. And this blessing convinced them that Thou art the Son of God, the Redeemer of the world.

Byzantine Icon of the XII. Sinai Monastery of st. Catherine