Easter

Introduction
Easter is a time that is celebrated by Catholics and most if not all of the denominations as a remembrance of the crucifixion of Christ.  It has intimate connection to the Jewish Passover, as this is the time at which Christ was killed.  It is ancient in origin, and near universal in practice.  It is one of two times in the year that people who never go to church go to church, and it has a secular aspect that is practiced by most people, the "Easter Bunny" and all of that, the eggs and what have you.
So why do churches of Christ have nothing to do with it?  It comes down to a question of authority in Christianity; whence it derives, and who has it.

Authority
After Jesus had arisen from the grave, he said,

"All authority has been given to Me in heaven and on earth.  Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all things that I have commanded you; and lo, I am with you always, even to the end of the age," Matthew 28:18-20.

While Jesus was here on earth before his death, he taught by the authority of God.  Now, all authority has been given to him, and he has told us to teach and observe all things that he has commanded us.  As this is a cursory examination of Easter, I won't go into many proofs, but suffice it to say that the rest of the New Testament, the letters as well as the gospels, were written by the authority of Jesus.
Now in Galatians 1:6-9 it says,

 "I marvel that you are turning away so soon from Him who called you in the grace of Christ, to a different gospel, which is not another; but there are some who trouble you and want to pervert the gospel of Christ.  But even if we, or an angel from heaven, preach any other gospel to you than what we have preached to you, let him be accursed.  As we have said before, so now I say again, if anyone preaches any other gospel to you than what you have received, let him be accursed."

This means that we are only authorized by Jesus to teach and to practice what he has taught us.  No man has any authority to teach or to practice anything as a tenet of Christianity which has not been given to us by Jesus.  If anyone chooses to do so, they are no longer following Christ, and are not accepted by him.

Remembering the death of Christ
Paul wrote,

"For I received from the Lord that which I also delivered to you: that the Lord Jesus on the same night in which He was betrayed took bread; and when He had given thanks, He broke it and said, 'Take, eat; this is My body which is broken for you; do this in remembrance of Me.'  In the same manner He also took the cup after supper, saying, 'This cup is the new covenant in My blood. This do, as often as you drink it, in remembrance of Me.'

"For as often as you eat this bread and drink this cup, you proclaim the Lord's death till He comes," 1 Corinthians 11:23-27.

We have been instructed, by the authority of Christ, how we are to remember his death.  This is by partaking of what is known as the Lord's Supper, week by week, on the first day of the week (the frequency of partaking of it is learned in another passage).

The Passover
The Passover was a commemoration of the Jewish people coming out of the land of Egypt, where they were slaves.  It was instituted by God, and they were to partake of it year by year, at the time instructed in the law, given through Moses.

The Passover (in which each family was to sacrifice a lamb) was a type, or shadow, a forerunner of the sacrifice of Christ.  The temple service and sacrificial system was an illustration of the coming Messiah, that he was to be a sacrifice for sin (it was to prepare the people, among other reasons, so that they might understand the Christ when he came).

When Christ was nailed to the cross, the law of Moses ended, and the law of Christ was instituted.  The things of the Old Testament (including the Ten Commandments) are useful for teaching, but they have no authority, no force of law.  They are no longer in effect (with the exception of the covenant He made with Noah upon leaving the ark), no longer recognized by God as the covenant in force.  He has removed it, and now recognizes the covenant which he has made with us through Christ.

The origin of Easter
There were some early Christians who kept the observance of the Passover, but did so as a celebration of Jesus; this is what Easter is.  This was an express violation of the law of Christ, and there was opposition to them on this ground.  Tertullian, in letters written c. 211 and c. 213 gives a defense against charges they were in violation of the passage from Galatians (quoted earlier in this essay), by saying they didn't need written authority, they were following tradition,

"If, for these and other such rules, you insist upon having positive Scripture injunction, you will find none.  Tradition will be held forth to you as the originator of them, custom as their strengthener, and faith as their observer."

As is wont to be the case, the bulk of the people did what made them happy, instead of  following what they were instructed by the Lord to do, and this is the view that won the day; thus we have Easter in the world.

At this point something needs to be mentioned in regards to where the "tradition" of which Tertullian spoke likely arose from; this will aid to an understanding of how it was that some Christians kept the Passover.

Under the law, the Jew was to keep certain festivals, including the Passover; to not keep them, carried with it the penalty that they were to be cut off from the people.  This was a requirement they were to keep, in order to remain pleasing to God.

Now Christianity comes, and these men are told that they no longer have to keep these feasts, they no longer have certain dietary restrictions, etc.  In fact, to keep these things as binding, as requirements of law, was now forbidden.  You had some older people who had spent their lives doing a thing they were required to do, which now they weren't to do anymore.  It was the case that there were Christians who understood this in their minds, but as a matter of conscience had trouble putting it into practice.

God understood this.  There is instruction given in the New Testament to the effect that if by conscience a man had trouble giving up a practice he had been accustomed to doing under the law, if he was too weak yet to give it up, that it was okay to continue in the practice - only he was not to bind it on others as a required practice.  Christ wanted the man to understand that he was now free from following it, but that if he would violate his conscience by doing so, he could continue in it (by violating his conscience, I mean that the man would believe that he was sinning against God by not following the practice he was accustomed to).

Undoubtedly, there were some early Christians who kept the Passover out of weakness, not because they were required to.  But we also can’t forget the fact that there are always men who want to do what they want to do, regardless of the law of Christ.  They wanted to keep the passover, but now it was “new”, in that they did it in memory of Christ. 

Summary
Christ has given to us how he wants us to remember his death, and it isn't by keeping a part of the law which he died to abolish.  Churches of Christ don't keep Easter, as it isn't from Jesus, but from man.

The time of Easter
Since Easter is really just an altering of the Passover, why isn’t it kept at the same time?  The Passover is always at a fixed time, but Easter moves around.  Early on, some kept it one way, and some kept it another, and it became such a matter of controversy that one of the main issues decided at the Council of Nicea in 325 A.D. was when to keep the festival.  It was decided that it should be kept on a Sunday, as this was the day the Lord was raised from the dead, and never on the day of the Passover, from opposition to Judaism, as the Jews had killed our Lord.  Therefore, it is always after the Passover, according to the first full moon after the vernal equinox.