Good Friday
Convention mainly. The calendar in a form as we know it was not introduced until many years after the death of christ. The calculations for that incident were incorrect.
Since 1 A.D. Christ's death was what made the change in the calendar.
Holy Thursday commemorates the last supper of Jesus and his disciples, in which he (according to the gospels) washed his disciples' feet, as a sign of service, and broke bread, calling it his body. It also commemorates his agony in the garden, as he reflected on the death that he knew was coming.In some churches it is known as Maundy Thursday.
Good Friday
The modern-day Jewish calendar has a leap year periodically that adds an extra month, so the Passover is a month after Christians recognize the day of Jesus' death in 2016. The memorial of Christ's death is celebrated by Christians according to the way the calendar was back in Jesus' day, and that he died on the first full moon after the Spring Equinox on Nisan 14.In 2016, the Spring Equinox is March 20, and the first full moon is the 23rd. That is why the 2016 Memorial of Jesus Christ's death is on March 23 and that would have been Nisan 14 back before 70 CE. The Jewish, however, start celebrating the Passover on April 22 in 2016, which is Nisan 14-15 according to the modern calendar. The modern-day Jewish calendar was instituted some time after the death of Christ and after the destruction of the temple.
The RLDS church is officially known as the Community of Christ. They are a Christian denomination which split with the Church of Jesus Christ of Latter-day Saints after the death of Joseph Smith in the 1840's. The Community of Christ is headquartered in Missouri.
The Church of Jesus Christ of Latter-day Saints (the correct name for the Mormon church) teaches first and foremost that Jesus Christ is our Savior and Redeemer, and that through faith in Christ and obedience to His commandments, we can live again in the presence of God after death. All other church doctrine supports that primary teaching. You can read about church doctrine by following the related links, below.
If you're referring to The Church of Jesus Christ of Latter-day Saints, Brigham Young. If the Community of Christ, Joseph Smith III.
The second president of the Church of Jesus Christ of Latter-day Saints (commonly called the "mormon" church) was Brigham Young. He was president of the Church from 1847 until his death in 1877.
Christianity is based on the death and resurrection of Jesus Christ. Jesus was put to death on a cross so Christian churches use a cross as their symbol.
The Catholic Church is incapable of absolving the Jews of killing Christ as they were no more responsible then every other human being who has ever lived. Every person (besides Our Blessed Lord and His Mother) have sinned, and with every sin we are responsible for Christ's death. Pope Paul VI issued a declaration during the Second Vatican Council repudiating the belief that the Jews are collectively responsible for Christ's death.