In countries which use the Gregorian calendar, New Year's Day is usually celebrated on 1 January. The order of months in the Roman calendar has been January to December since King Numa Pompilius in about 700 BC, according to Plutarch and Macrobius. However, Roman writers identified years by naming the year's consuls, who did not enter office on 1 January until 153 BC. Since then 1 January has been the first day of the year, except during the Middle Ages when several other days were the first (1 March, 25 March, Easter, 1 September, 25 December). With the expansion of Western culture to the rest of the world during the twentieth century, the 1 January date became global, even in countries with their own New Year celebrations on other days (e.g., China and India). At present, the celebration of the New Year is a major event worldwide. Many large-scale events are held in major cities around the world, with many large fireworks events on New Year's Eve (31 December). Sydney launched over 80,000 fireworks at midnight, and had more than one and a half million attendees; it was also the most-watched event on television worldwide last year. In Valparaiso upwards of two million visitors witnessed the largest fireworks display in a natural setting; a total of more than 21 kilometers of fireworks on the bay, from the commercial port city of Valparaiso to Concon, Chile, all in 25 minutes of entertainment. London's New Year celebrations centre around the London Eye, with an impressive fireworks display while Big Ben strikes midnight. In New York, the celebration is focused around a large crystal ball that descends in a one minute countdown in Times Square. Edinburgh plays host to one of the world's largest Hogmanay events. The celebrations last for four days and attract visitors from around the globe to take part in street parties and attend concerts. In the culture of Latin America there are a variety of traditions and superstitions surrounding these dates as omens for the coming year. January remains a symbol of the New Year's celebration. According to the Christian tradition, 1 January coincides with the circumcision of Christ (eight days after birth), when the name of Jesus was given to him (Luke 2: 21).

Maundy Thursday, also known as Holy Thursday, Great and Holy Thursday, and Thursday of Mysteries, is the Christian feast or holy day falling on the Thursday before Easter that commemorates the Last Supper of Jesus Christ with the Apostles. It is the fifth day of Holy Week, and is preceded by Holy Wednesday and followed by Good Friday. The date is always between 19 March and 22 April inclusive. These dates in the Julian calendar, on which Eastern churches in general base their calculations of the date of Easter, correspond throughout the twenty-first century to 1 April and 5 May in the more commonly used Gregorian calendar. The Mass of the Lord's Supper initiates the Easter Triduum, the three days of Friday, Saturday and Sunday that commemorate the Passion, Death and Resurrection of Jesus. It is normally celebrated in the evening, when according to Jewish tradition Friday begins.

Good Friday, also called Holy Friday, Black Friday, or Great Friday, is a holiday observed primarily by adherents to Christianity commemorating the crucifixion of Jesus 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 often coincides with the Jewish observance of Passover. Based on the 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.

International Workers' Day (a name used interchangeably with may day) is a celebration of the social and economic achievements of the international labor movement. May Day commonly sees organized street demonstrations and street marches by millions of working people and their labour unions throughout most of the countries of the world.

According to the belief of Christians of the Catholic Church, the Eastern Orthodox, and Oriental Orthodox churches and by some Anglicans, the Assumption of Mary was the bodily taking up of the Virgin Mary into Heaven at the end of her life. The Catholic Church teaches as dogma that Mary, "having completed the course of her earthly life, was assumed body and soul into heavenly glory." This doctrine was dogmatically and infallibly defined by Pope Pius XII on November 1, 1950, in his Apostolic Constitution Munificentissimus Deus. This belief is known as the Dormition by the Orthodox. In the churches which observe it, the Assumption is a major festival, commonly celebrated on August 15. In many countries it is a Catholic Holy Day of Obligation. In his August 15, 2004, homily given at Lourdes, Pope John Paul II quoted John 14:3 as one of the scriptural bases for understanding the dogma of the Assumption of Mary. In this verse, Jesus tells his disciples at the Last Supper, "If I go and prepare a place for you, I will come again, and will receive you to myself; that where I am, you may be there also." According to Catholic theology, Mary is the pledge of the fulfillment of Christ's promise.

Christmas Eve is the day before Christmas Day, a widely celebrated holiday commemorating the birth of Jesus of Nazareth. It is a culturally significant celebration for most of the Western world and is widely observed as a full or partial holiday in anticipation of Christmas. In Western culture, Christmas Eve is celebrated on December 24. However, the Coptic, Serbian, Russian, Macedonian, and Georgian Orthodox Churches, as well as the Greek Orthodox Church of Jerusalem, use the Julian calendar, which is currently thirteen days behind the Gregorian calendar, so Christmas Eve for the adherents of those Churches coincides with January 6 of the following year in the Gregorian calendar.

Christmas or Christmas Day is an annual Christian holiday commemorating the birth of Jesus Christ. It is celebrated on December 25, but this date is not known to be Jesus' actual birthday, and may have initially been chosen to correspond with either the day exactly nine months after some early Christians believed Jesus had been conceived, a historical Roman festival, or the date of the northern hemisphere's winter solstice. Christmas is central to the Christmas and holiday season, and in Christianity marks the beginning of the larger season of Christmastide, which lasts twelve days