The Christian holiday of Easter has its prototype in the Old Testament. An Old Testament holiday with a similar name (Passover in Hebrew, Easter in Aramaic) It was celebrated in memory of the departure of the God-chosen people from Egypt. The key moment of the Exodus was the slaughter of the immaculate lamb to save the firstborn from death. It was a prophetic prototype of another, higher Sacrifice, which gave new life to all mankind. Such a Sacrifice was made by the Incarnate God on the Cross of Calvary for all people.
Easter is one of the oldest church holidays. It was definitely already celebrated in the second century; however, there is a possibility that the apostles, gathering on the day of the Jewish Passover, were already remembering the sufferings of Christ, and not the exit of ancient Israel from Egypt. The exact time of Easter celebration was determined by the First Ecumenical Council, which ordered all Christians to celebrate Easter on the 1st Sunday after the full moon, which should occur after the vernal equinox.
The Easter celebration day currently (in the 21st century), depending on the year, ranges from April 4 to May 8 of the new style.

Like the innocent lamb, Jesus Christ was a perfect Man without sin or blemish, for in Him the human nature was united with the Divine. Devoid of any sin, He voluntarily gave Himself up to suffer for the salvation of mankind. By His suffering, He redeemed the human race from the sinful curse and the power of death.
Possessing the Holiness of God, He became above death: "Joseph buried Him as a dead man, but, buried as a man, He disarmed death as God" (St. Hesychius of Jerusalem). Having descended into hell, He came out of it, because no guilt was found in Him.

"Death! Where is your sting?! Hell! where is your victory?!" exclaims the Apostle Paul. "Christ is risen, and hell has been cast down! Christ is risen, and the demons have fallen! Christ is risen, and the angels rejoice! Christ is risen, and life is triumphant! Christ is risen, and no one is dead in the grave! For Christ, having risen from the tomb, is the firstborn of the dead," says St. John. John Chrysostom.