According to Wikipedia Good Friday Means:
"Good Friday, also known as Holy Friday, Black Friday, Great Friday, is a holiday observed primarily by Christians commemorating the crucifixion of Jesus Christ, his death as believed by Christians at Calvary, and his Resurrection from the grave. The holiday is observed during Holy Week as part of the Paschal Triduum on the Friday preceding Easter Sunday, and often coincides with the Jewish observance of Passover.
Based on the Christian scriptural details of the Sanhedrin Trial of Jesus, the Crucifixion of Jesus was most probably on a Friday. The estimated year of Good Friday is AD 33, by two different groups, and originally as AD 34 by Isaac Newton via the differences between the Biblical and Julian calendars and the crescent of the moon. A third method, using a completely different astronomical approach based on a lunar Crucifixion darkness and eclipse model (consistent with Apostle Peter's reference to a "moon of blood" in Acts 2:20) arrives at the same date, namely Friday April 3, AD 33."