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).

According to legend Devota (Dévote in French), a young Christian girl, native of Corsica, would have been martyred by the prefect Barbarus under the Diocletian and Maximian Emperors on a date that one could place in 303 or 304. Her body was stolen by night by Christian believers, put into a boat, transported to Monaco and buried in the chapel of a small valley called "des Gaumates", near the port, on 27 January of the same year.

Easter (Greek: Πάσχα) is the most important annual religious feast in the Christian liturgical year. According to Christian scripture, Jesus was resurrected from the dead on the third day of his crucifixion. Christians celebrate this resurrection on Easter Day or Easter Sunday (also Resurrection Day or Resurrection Sunday), two days after Good Friday and three days after Maundy Thursday. The chronology of his death and resurrection is variously interpreted to be between AD 26 and AD 36. Easter also refers to the season of the church year called Eastertide or the Easter Season. Traditionally the Easter Season lasted for the forty days from Easter Day until Ascension Day but now officially lasts for the fifty days until Pentecost. The first week of the Easter Season is known as Easter Week or the Octave of Easter. Easter also marks the end of Lent, a season of fasting, prayer, and penance. Easter is a moveable feast, meaning it is not fixed in relation to the civil calendar. The First Council of Nicaea (325) established the date of Easter as the first Sunday after the full moon (the Paschal Full Moon) following the vernal equinox. Ecclesiastically, the equinox is reckoned to be on March 21. The date of Easter therefore varies between March 22 and April 25. Eastern Christianity bases its calculations on the Julian Calendar whose March 21 corresponds, during the twenty-first century, to April 3 in the Gregorian Calendar, in which calendar their celebration of Easter therefore varies between April 4 and May 8. Easter is linked to the Jewish Passover not only for much of its symbolism but also for its position in the calendar. Relatively newer elements such as the Easter Bunny and Easter egg hunts have become part of the holiday's modern celebrations, and those aspects are often celebrated by many Christians and non-Christians alike.

Easter (Greek: Πάσχα) is the most important annual religious feast in the Christian liturgical year. According to Christian scripture, Jesus was resurrected from the dead on the third day of his crucifixion. Christians celebrate this resurrection on Easter Day or Easter Sunday (also Resurrection Day or Resurrection Sunday), two days after Good Friday and three days after Maundy Thursday. The chronology of his death and resurrection is variously interpreted to be between AD 26 and AD 36. Easter also refers to the season of the church year called Eastertide or the Easter Season. Traditionally the Easter Season lasted for the forty days from Easter Day until Ascension Day but now officially lasts for the fifty days until Pentecost. The first week of the Easter Season is known as Easter Week or the Octave of Easter. Easter also marks the end of Lent, a season of fasting, prayer, and penance. Easter is a moveable feast, meaning it is not fixed in relation to the civil calendar. The First Council of Nicaea (325) established the date of Easter as the first Sunday after the full moon (the Paschal Full Moon) following the vernal equinox. Ecclesiastically, the equinox is reckoned to be on March 21. The date of Easter therefore varies between March 22 and April 25. Eastern Christianity bases its calculations on the Julian Calendar whose March 21 corresponds, during the twenty-first century, to April 3 in the Gregorian Calendar, in which calendar their celebration of Easter therefore varies between April 4 and May 8. Easter is linked to the Jewish Passover not only for much of its symbolism but also for its position in the calendar. Relatively newer elements such as the Easter Bunny and Easter egg hunts have become part of the holiday's modern celebrations, and those aspects are often celebrated by many Christians and non-Christians alike.

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.

The Christian doctrine of the Ascension holds that Jesus ascended to heaven in the presence of his Eleven Apostles following his resurrection, and that in heaven he sits at the right hand of God the Father. Jesus died circa 30. In the Epistle to the Romans (c. 56-57), Saint Paul describes Christ as in heaven and in the abyss[Rom. 10:5-7] the earliest Christian reference to Jesus in heaven. The most influential account of the Ascension, and according to the two-source hypothesis the earliest, is in Acts of the Apostles[1:1-11] where Jesus is taken up bodily into heaven forty days after his resurrection as witnessed by his apostles, after giving the Great Commission with a prophecy to return. In the Gospel of Luke, the Ascension takes place on Easter Sunday evening. The Gospel of John (c. 90-100) refers to Jesus returning to the Father.[Jn. 20:17] In the First Epistle of Peter (c. 90-110), Jesus has ascended to heaven and is at God's right side. Pet. 3:21-22] The Epistle to the Ephesians (c. 90-100) refers to Jesus ascending higher than all the heavens.[Eph. 4:7-13] The First Epistle to Timothy (c. 90-140) describes Jesus as taken up in glory.[Tim. 3:16] The traditional ending of Mark[16:19] includes a summary of Luke's resurrection material and describes Jesus as being taken up into heaven and sitting at God's right hand. The imagery of Jesus' Ascension is related to the broader theme of his exaltation and heavenly welcome, derived from the Hebrew Bible. The image of Jesus rising bodily into the heavens reflects the ancient view that heaven was above the earth. Belief in the Ascension of Jesus is found in the Nicene Creed, and is affirmed by Christian liturgy and, in the West, by the Apostles' Creed. The Ascension implies Jesus' humanity being taken into heaven. Ascension Day, celebrated 40 days after Easter, is one of chief feasts of the Christian year. The feast dates back at least to the later 300s, as is widely attested. The canonical account of Jesus ascending bodily into the clouds contrasts with the gnostic tradition, by which Jesus was said to transcend the physical realm and return to his home in the spirit world. It also contrasts with the beliefs of Docetism, in which matter is intrinsically evil and Jesus was said to have been pure spirit.

Corpus Christi (Latin for Body of Christ) is a Western Catholic feast. It is also celebrated in some Anglican and Lutheran churches. It honors the Eucharist, which believers consider to be the actual body and blood of Christ, and as such it does not commemorate a particular event in Jesus' life. It is held on the Thursday after Trinity Sunday or, in some places, on the following Sunday. Its celebration on a Thursday is meant to associate it with Jesus' institution of the Eucharist during the Last Supper, commemorated on Maundy Thursday, and this is the first free Thursday after Paschaltide. In the Ordinary Form of the Catholic Church, the feast is officially known as the Solemnity of the Most Holy Body and Blood of Christ. In many English-speaking countries, Corpus Christi is transferred to the Sunday after Trinity Sunday by both Catholics and Anglicans. At the end of the Mass, it is customary to have a Procession of the Blessed Sacrament (often outdoors), followed by Benediction of the Blessed Sacrament.

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.

All Saints' Day (in the Catholic Church officially the Solemnity of All Saints and also called All Hallows or Hallowmas), often shortened to All Saints, is a solemnity celebrated on 1 November in Western Christianity, and on the first Sunday after Pentecost in Eastern Christianity, in honour of all the saints, known and unknown. In terms of Western Christian theology, the day commemorates all those who have attained the beatific vision in Heaven. In the Roman Catholic Church, the next day, All Souls' Day, specifically commemorates the departed faithful who have not yet been purified and reached heaven. It is a national holiday in many historically Catholic countries.

The Immaculate Conception is, according to Roman Catholic doctrine, the conception of the Virgin Mary without any stain ("immacula" in Latin) of original sin. It is one of the four dogmas in Roman Catholic Mariology. Under this aspect Mary is sometimes called the Immaculata (the Immaculate One), particularly in artistic contexts. The dogma states that, from the first moment of her existence, Mary was preserved by God from the lack of sanctifying grace that afflicts mankind and that she was instead filled with divine grace. It is further said by Catholics that she lived a life completely free from sin. Belief in Mary's immaculate conception in the womb of her mother, through sexual intercourse, should not be confused with the doctrines of the virginal conception of her son Jesus, known as the Annunciation and the Virgin Birth. The feast of the Immaculate Conception, celebrated on 8 December, was established as a universal feast in 1476 by Pope Sixtus IV. He did not define the doctrine as a dogma, thus leaving Roman Catholics free to believe in it or not without being accused of heresy; this freedom was reiterated by the Council of Trent. The existence of the feast was a strong indication of the Church's belief in the Immaculate Conception, even before its 19th century definition as a dogma. The Immaculate Conception was solemnly defined as a dogma by Pope Pius IX in his constitution Ineffabilis Deus on 8 December 1854. The Catholic Church teaches that the dogma is supported by Scripture (e.g., Mary's being greeted by the Angel Gabriel as "full of grace") as well as either directly or indirectly by the writings of Church Fathers such as Irenaeus of Lyons and Ambrose of Milan. Catholic theology maintains that since Jesus became incarnate of the Virgin Mary, it was fitting that she be completely free of sin for expressing her fiat. In 1904 Pope Saint Pius X also addressed the issue in his Marian encyclical Ad Diem Illum on the Immaculate Conception. In the Catholic Church the Solemnity of the Immaculate Conception is a Holy Day of Obligation, except where conferences of bishops have decided, with the approval of the Holy See, not to maintain it as such. It is a public holiday in some countries where Roman Catholicism is predominant.

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