Today is Passover. Well before the term “Easter” was in use, most early Christians remembered the death & resurrection of Jesus Christ (Ἰησοῦ Χριστοῦ), the Lamb of God, on Pascha (Greek word for Passover) which fell on the Sunday after Passover in the pre-Nicene era.
However, according to his protege Ireneaus, the famous martyr Polycarp, himself a disciple of the apostle John and the bishop of Smyrna, insisted that John held Pascha on Nisan 14 of the Jewish calendar which is Passover. John, of course, leaned against Christ during the Last Supper (John 13:25) which is forever associated with Passover (Matt 26:17-19). So, assuming Irenaeus is correct, John may have been trying to perpetuate the memory of that event? The church in Smyrna and throughout Asia Minor held Pascha on Passover at least until the Council of Nicaea in 325.
Pascha could be both a solemn and celebratory event.
Here are some quotes from early Christians:
“Finally, [what unbelieving husband] will without anxiety endure her absence all the night long at the Pascha solemnities?” [Tertullian 205 AD]
“We consider fasting or kneeling in worship on the Lord’s Day [Sunday] to be unlawful. We rejoice in the same privilege also from Pascha to Pentecost.” [Tertullian 211 AD]
“You have sent to me, most faithful and accomplished son, in order to inquire what is the proper hour for bringing the fast to a close on the day of Pascha. You say that there are some of the brethren who hold that it should be done at cockcrow. However, others say it should end at nightfall…. It will be cordially acknowledged by all that those who have been humbling their souls with fasting should immediately begin their festal joy and gladness at the same hour as the resurrection…. However, no precise account seems to be offered in [scripture] as to the hour at which He rose.” [Dionysius of Alexandria 262 AD]
“The other party keeps the day of the Lord’s passion as one replete with sadness and grief. They hold that it would not be lawful to celebrate the Lord’s mystery of the Passover at any other time but on the Lord’s Day.” [Anatolius 270 AD]