During the Resurrection Liturgy according to the Coptic Orthodox rite, we have what we call the 'Resurrection Enactment' which is essentially a dialogue in chant that takes place between a deacon standing outside the sanctuary (who represents an Angel accompanying the Lord Christ), and the priest who is inside the sanctuary (who represents the Cherubum guarding the gates of paradise). The following dialogue then takes place:
Angel: Christ is Risen.
Cherubim: Indeed He is Risen.
Angel: Open your gates O you Kings, and be lifted up you everlasting doors (x2). Open your gates O you Kings, and be lifted up you everlasting doors, that the King of Glory may enter!
Cherubim: Who is the King of Glory?
Angel: The Almighty Lord, Who is strong, powerful, and mighty in battles; He is the King of Glory!
The context of this enactment (taking place during the Resurrection Liturgy) implies that the dialogue took place upon Christ's ascent to paradise immediately proceeding His descent into Hades (and hence not his ascent into Heaven after 40 days). Another contextual factor that reinforces this is the fact that, according to our rite, whilst the deacons outside the sanctuary represent the Angels accompanying the Lord, the congregation represent the righteous saints who have been delivered from Hades. The purpose of the 'ascension' being commemorated is thus not the Seating at the Right Hand of the Father, but simply the leading of the liberated saints to their new home--Paradise.
According to the Syriac and Armenian rites, however, this dialogue is commemorated on the eve of the Feast of the Ascension, and both traditions seem to be based on a tradition related by St Dionysius the Arepagite.
I personally don't think it problematic to conclude that this dialogue took place twice, but I am curious to know if it is commemorated in the EO tradition and, if so, on what particular occasion: the Feast of the Resurrection or the Feast of the Ascension?