The word translated “Easter” in the following passages is literally Passover [Gr. pascha]. This does not refer to the Jewish Passover but to the Christian Passover.
[WRITTEN TO CHRISTIANS:] You have your own registers, your own calendar. You have nothing to do with the joys of the world. In fact, you are called to the very opposite—for the world will rejoice, but you will mourn.” Tertullian (c. 212, W), 3.101.
If the apostle has erased all devotion absolutely of “seasons, days, months, and years,” why do we celebrate Easter by an annual rotation in the first month? Why in the fifty ensuing days do we spend our time in all exultation? Why do we devote to stations the fourth and sixth days of the week, and to fasts the Preparation Day [i.e., Good Friday]? Anyhow, you sometimes continue your station even over the Sabbath—a day never to be kept as a fast except at the Easter season. Tertullian (c. 213, W), 4.112.
We ourselves are accustomed to observe certain days. For example, there is the Lord’s Day, the Preparation, Easter, and Pentecost. . . . However, the majority of those who are accounted believers are not of this advanced class [i.e., those who focus on Christ every day]. Rather, they require some sensible memorials to prevent spiritual things from passing completely away from their minds. For they are either unable or unwilling to keep every day in this manner. Origen (c. 248, E), 4.647, 648.
Compare the festivals that are observed among us (which have been described above) with the public feasts of Celsus and the pagans. Would you not say that ours are much more sacred observances than those feasts in which the lust of the flesh runs riot and leads to drunkenness and debauchery? Origen (c. 248, E), 4.648.
[REFERRING TO THE EASTER VIGIL:] Then the middle of the heavens will be laid open in the dead and darkness of the night so that the light of the descending God may be manifest in all the world. . . . This is the night that is celebrated by us in watchfulness on account of the coming of our King and God. Lactantius (c. 304–313, W), 7.215.
Brethren, observe the festival days. First of all, there is the birthday that you are to celebrate on the twenty-fifth of the ninth month [i.e., December 25]. After that, let the Epiphany be to you the most honored, in which the Lord made to you a display of His own divinity. And let that feast take place on the sixth of the tenth month [i.e., January 6]. After that, the fast of Lent is to be observed by you as containing a memorial of our Lord’s manner of life and teaching. But let this solemnity be observed before the fast of Easter, beginning from the second day of the week and ending at the Day of the Preparation. After those solemnities, breaking your fast, begin the holy week of Easter, all of you fasting in this week with fear and trembling. Apostolic Constitutions, (compiled c. 390, E), 7.443.
From [Easter], count forty days, from the Lord’s day until the fifth day of the week, and celebrate the feast of the Ascension of the Lord. Apostolic Constitutions (compiled c. 390, E), 7.448.