That is incorrect. His resurrection was stated as being on the first day of the week, which is Sunday. Now, you also have to consider in antiquity the day was reckoned to begin and end at Sunset. We see this today reflected in Jewish practices where their Sabbath is from Sunset on Friday to Sunset on Saturday.
Our Lord said “destroy this temple and I will build it again in 3 days.” Sunset usually happens around the 12th hour; Christ the Only Begotten Son and Divine Logos, was crucified at the 6th hour and died at the ninth hour. That is day one. Day two, God the Son, having remade man in His own image through His victory on the Cross (as indicated by the famous quote from Pontius Pilate, “Ecce homo”, and despoiling Hell by freeing those captive there who chose to follow him to Heaven (thus, people from before the time of Christ are not destined to remain in Hell until the last judgement, for our God is love, and is infinitely merciful), rested in a tomb, just as He had rested following creation in Genesis 1. Day three, when the myrhh bearing women arrived in the morning (hence the custom of early morning services in some churches), the tomb was empty, meaning that at some point on that day prior to their arrival, our Lord rose from the grave. The angels who created the women had shining, luminous raiments, which combined with the triumph of life over death, is prophesied in Genesis 1, with “Let there be light.”
Genesis 1 is much more important than most people realize, for it is not just an account of the creation of the universe, which is interesting, but also of the Passion and Resurrection of Jesus Christ, by whom all things in the Universe were made, which is more interesting, because The Only Begotten Son and Word of God became incarnate, entering into His own creation, to free mankind from death, and through His own death, to show us how to be human. (Fr. John Behr, while he was dean of St. Vladimir’s Seminary, liked to stress how all of the great heresies tried to bypass that concept, because it is a “hard saying”, but a careful exegesis of the Gospels will show it to be the truth, and it is also what the early Church Fathers believed, and is reasonable, given divine omnipotence, and the experience of the church has been fighting off various heresies like Docetism, Arianism, Unitarianism, and Nestorianism, which either deny the Humanity of Christ, the deity of Christ, or,the union of His Divinity with His Humanity, acquired from being born by a virgin, Mary, meeting the three criteria Anglicans use for doctrine (Scripture, Tradition and Reason), and the fourth criterion John Wesley added, experience, which logic dictates can be collective as well as individual; this forms the Wesleyan Quadrilateral which is widely used by Protestants for purposes of dogmatic theology.
This is a common conspiracy theory about Easter, but it falls apart when one takes note of the fact that most Christians refer to the holiday as Pascha or a derivative word (for example, the Dutch call it Passen), all of which are related to the English word passover, which for some reason we interpret purely in the sense of Judaism, when there is plenty of scriptural material to suggest the Crucifixion is the new, final, ultimate Passover.
The use of the word Easter to refer to Pascha, or, as it is most properly titled, The Feast of the Resurrection, began with the Christianization of Northwest Europe, but the Dutch use of Passen, and other examples, will show that almost all people who call it Easter are native English speakers. Prior to that time, in the first few centuries of Christianity, it was called Pascha, and this term is used universally by the Eastern Orthodox, the Oriental Orthodox, the Assyrian Church of the East, and non-English speaking Maronites, and is also used in the Latin Rites of the Roman Catholic church. Indeed, the period from Good Friday to Easter Sunday is called the Pachal Triduum.
For that matter, Pentecost, on which is celebrated, based on scripture, the procession of God the Holy Spirit to the Disciples at the Third Hour, is commonly called “Whitsunday” in English, because wheat was used to symbolize the tongues of fire.
The Nicene Paschalion was one of two in use in the early church; the other, popular in the East, was the Quartodecimian, which celebrated Pascha on the 14th of Nisan. However, concerns had emerged by the Council of Nicea that the Jews had changed their method of calculating their calendar (something confirmed by the Karaites, who rejected the Rabinnical teachings in the Talmud and followed only the text of the Old Testament. Consequently, the council made a canonical decree that set the date of Pascha as you describe.
The custom of Sunrise services on Easter is not universal, although the office of Lauds in some monasteries is observed at Sunrise. Most Christians in the West have, since the legalization of Christianity, celebrated Pascha in the morning; this is also the practice of the Armenian Orthodox. Most Orthodox Christians celebrate Pascha exclusively at night, traditionally midnight, although some churches for reasons of safety have moved the service back to 8 PM, which is fine, because it is still Sunday according to the ancient system of reckoning when days begin and end (liturgical days, interestingly, begin and end at the service of Vespers, which normally happens at Sunset, but which can happen earlier; the Eastern Orthodox have a Vesperal Divine Liturgy in the morning of Holy Saturday, and the Roman Catholics had a similar service until 1955, when Pope Pius XII made arbitrary and capricious changes to an ancient liturgy, used in a similar way by Roman Catholics and Eastern Orthodox, that dated back to Pope St. Gregory the Great, in the late 6th century, centuries before the Great Schism in which the Roman Catholic Church, which was innovating and experiencing corruption, excommunicated the Eastern Orthodox for their fidelity.
In the 16th century, St. Jan Hus and St. Jerome of Prague, recognized as martyrs by the Eastern Orthodox Church, started the Protestant reformation in an attempt to restore to the country we now call the Czech Republic the vernacular liturgy and communion in both kinds, which they had enjoyed under the Orthodox Church until Austria conquered the land and forcibly converted everyone to the Roman Rite of the Catholic Church. St. Jan Hus was burned at the stake, but the church he founded is still around, the Moravian Church, miraculously, and Martin Luther took up his cause, created an unstoppable Reformation, and the Roman Catholic church in turn had to reform itself to prevent more countries from leaving it, which it did in the Counter Reformation. God works in mysterious ways, and thus one can see how an aggrieved Eastern Orthodox founded Protestantism, protesting practices of the Roman Catholic Church, that after his martyrdom became a success, reforming the churches of several countries and forcing the Roman Catholics to get their house in order and put an end to corrupt popes like Alexander VI Borgia or Leo X, and to practices like the sale of indulgences.
