Significance
Good Friday is a religious holiday, observed primarily by Christians, commemorating the crucifixion of Jesus Christ and his death at Calvary. The holiday is observed during Holy Week as part of the Paschal Triduum on the Friday preceding Easter Sunday, and may coincide with the Jewish observance of Passover. It is also known as Holy Friday, Great Friday, Black Friday, or Easter Friday, though the last term properly refers to the Friday in Easter week.
Good Friday is a widely-instituted legal holiday in many national governments around the world, including in most Western countries (especially among Catholic nations and majority-Catholic countries) as well as in 12 U.S. states. Some governments have laws prohibiting certain acts that are seen as profaning the solemn nature of the day.
History
Based on the details of the canonical gospels, the Crucifixion of Jesus was most likely to have been on a Friday (the day before the Jewish Sabbath) (John 19:42). The estimated year of the Crucifixion 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), points to Friday, 3 April AD 33.
Determination of Date
When Chaturdashi with sunrise falls on 21st March or immediately after 21st March then the Sunday which follows is termed as Easter Sunday. Good Friday is celebrated on the Friday which falls two days before Easter Sunday. If Chaturdashi falls at sunrise on Sunday then next Sunday becomes Easter Sunday and accordingly good Friday is celebrated.
How to Celebrate
The Catholic Church treats Good Friday as a fast day, which in the Latin Church is understood as having only one full meal (but smaller than a regular meal) and two collations (a smaller repast, two of which together do not equal one full meal) and on which the faithful abstain from eating meat. This is why many places have the typical 'Fish Friday'. In countries where Good Friday is not a day of rest from work, the afternoon liturgical service is usually put off until a few hours after the recommended time of 3 pm.
Services on the day-
The Roman Rite has no celebration of Mass between the Lord's Supper on Holy Thursday evening and the Easter Vigil unless a special exemption is granted for rare solemn or grave occasions by the Vatican or the local bishop. The only sacraments celebrated during this time are Baptism (for those in danger of death), Penance, and Anointing of the Sick. While there is no celebration of the Eucharist, it is distributed to the faithful only in the Service of the Passion of the Lord, but can also be taken at any hour to the sick who are unable to attend this service. During this period crosses, candlesticks, and altar cloths are removed from the altar which remains completely bare. It is also customary to empty the holy water fonts in preparation of the blessing of the water at the Easter Vigil. Traditionally, no bells are rung on Good Friday or Holy Saturday until the Easter Vigil.
The Celebration of the Passion of the Lord takes place in the afternoon, ideally at three o'clock, but for pastoral reasons a later hour may be chosen. The vestments used are red (more commonly) or black (more traditionally). Before 1970, vestments were black except for the Communion part of the rite when violet was used. Before 1955 black was used throughout. If a bishop or abbot celebrates, he wears a plain mitre (mitra simplex).