to sbg4evr,
I am Orthodox and the church teaches that though it was during the passover the Lords supper was first celabrated after Jesus rose he celabrated the resurrection with the disciples on the first day of the week. He broke bread with them. Since also many new Christians were not only Jews they had no tradition of the Jewish passover. The Jews of that time who followed Christ did still celabrate both but as time went on the converts were less and less. Then Paul also taught that we should not worry about what holiday someone does or does not celabrate or how. For Christians the communion meal is the celabration of the lamb of God for us. For he is the fullfiment of all that came before. So for many new Christians the first day of the week became as it states in the bible the day Christians came together to worship, praise and partake of the communion.