From a contemporary Orthodox theologian, Fr. Thomas Hopko, Dean Emeritus of St. Vladimir's Orthodox Theological Seminary in Crestwood, NY:
In the Orthodox Church the feast of Easter is officially called Pascha, the word which means the Passover. It is the new Passover of the new and everlasting covenant foretold by the prophets of old. It is the eternal Passover from death to life and from earth to heaven. It is the Day of the Lord proclaimed by God's holy prophets, "the day which the Lord has made" for his judgment over all creation, the day of His final and everlasting victory. It is the Day of the Kingdom of God, tile day "which has no night" for "its light is the Lamb" (Rev 21:22-25).
The celebration of Easter in the Orthodox Church, therefore, is once again not merely an historical reenactment of the event of Christ's Resurrection as narrated in the gospels. It is not a dramatic representation of the first Easter morning." There is no "sunrise service" since the Easter Matins and the Divine Liturgy are celebrated together in the first dark hours of the first day of the week in order to give men the experience of the "new creation" of the world, and to allow them to enter mystically into the New Jerusalem which shines eternally with the glorious light of Christ, overcoming the perpetual night of evil and destroying the darkness of this mortal and sinful world:
Shine! Shine! O New Jerusalem! The glory of the Lord has shone upon you! Exult and be glad O Zion! Be radiant 0 Pure Theotokos, in the Resurrection of your son!
[source: Hopko, Thomas. The Orthodox Faith, Vol. 2: Worship. http://www.oca.org/OCchapter.asp?SID=2&ID=76 ]