The faith being celebrated is the same event
The Church is celebrating Christ’s Resurrection from the dead. The date difference comes from calendar calculation, not from a different Resurrection.
But now Christ is risen from the dead, and has become the firstfruits of those who have fallen asleep.
The Coptic Orthodox Church belongs to the Alexandrian tradition that has long served the calculation of Pascha. The date is connected to the spring equinox, the full moon, Sunday, and the inherited relationship to Passover. Because calendars and calculations differ, the civil date often differs too.
How the date shapes worship
Holy Week, Good Friday, Bright Saturday, and the Resurrection Liturgy move according to the date of the Resurrection Feast. The date therefore shapes the fasting calendar, the services, and the journey from Great Lent to Pascha.
That is why the question matters beyond curiosity. The date determines when Great Lent begins, when Holy Week is prayed, and when the Church celebrates the Resurrection Liturgy. It also affects the Apostles’ Fast because that fast begins after Pentecost.
How to read the difference
The calculation may be complex, but the worship is simple in purpose: the Church prepares for and celebrates the risen Christ. The calendar difference should lead the reader back to Pascha itself. The Church fasts, prays, keeps Holy Week, and proclaims that Christ is risen from the dead.