It matters not whether Jesus was raised up on Saturday after sunset or just before dawn on Sunday.
Christians are free to celebrate the resurrection and take communion on whatever day suits them - there is no legal ordinance to worship on a Jewish sabbath day.
None whatsoever.
As for "Easter" that is Roman Catholic and Eastern Orthodox traditions requiring extra acknowledgement to the death, burial and resurrection of our Lord and Saviour.
But Christians do in fact celebrate "Easter" every Sunday when we partake of Holy Communion and remember the atoning sacrifice of Jesus and his resurrection.
For it is the resurrection of the dead that our faith and overcoming the world is all about - the great reward to come.
1Cor 15:1 Now I would remind you, brothers, of the gospel I preached to you, which you received, in which you stand,
2 and by which you are being saved, if you hold fast to the word I preached to you—unless you believed in vain.
3 For I delivered to you as of first importance what I also received: that Christ died for our sins in accordance with the Scriptures,
4 that he was buried, that he was raised on the third day in accordance with the Scriptures,
1Cor 15:12 Now if Christ is proclaimed as raised from the dead, how can some of you say that there is no resurrection of the dead?
13 But if there is no resurrection of the dead, then not even Christ has been raised.
14 And if Christ has not been raised, then our preaching is in vain and your faith is in vain.
15 We are even found to be misrepresenting God, because we testified about God that he raised Christ, whom he did not raise if it is true that the dead are not raised.
16 For if the dead are not raised, not even Christ has been raised.
17 And if Christ has not been raised, your faith is futile and you are still in your sins.
18 Then those also who have fallen asleep in Christ have perished.
