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).

The Day of Remembrance for Truth and Justice (Spanish: Día de la Memoria por la Verdad y la Justicia) is a public holiday in Argentina, commemorating the victims of the military dictatorship known as the National Reorganization Process (Proceso de Reorganización Nacional). It is held on 24 March, the anniversary of the coup d'état of 1976 that brought the military junta to power. The commemoration was sanctioned as Law 25633 by the Argentine National Congress on 1 August 2002, and promulgated by the Executive Branch on 22 August of the same year. However, it was not implemented as a public national holiday until 2006. The 30th anniversary of the coup was marked by massive demonstrations.

Malvinas Day (Spanish: Día de Malvinas), officially Day of the Veterans and Fallen of the Malvinas War (Día del Veterano de Guerra y de los Caídos en la Guerra de las Malvinas) is a public holiday in Argentina, celebrated each year on April 2. The islands are known in the English-speaking world as the Falkland Islands. The holiday is a tribute to Argentina's fallen soldiers in the Falklands War (Guerra de las Malvinas), which began with the Argentine occupation of the islands on April 2, 1982. 649 Argentinians, of which 633 military and 16 civilians lost their lives during the 74-days' campaign. Malvinas Day was first introduced on November 22, 2000, and replaced the Day of Argentine Sovereignty over the Malvinas, Sandwich and South Atlantic Islands (Día de los Derechos Argentinos sobre las Islas Malvinas, Sandwich y del Atlántico Sur) observed on June 10, which had until then commemorated the appointment by Buenos Aires of Luis Vernet as governor of the islands in 1829.

Maundy Thursday, also known as Holy Thursday, Covenant Thursday, Great & 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 Good Friday, Holy Saturday and Easter 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.

The May Revolution (Spanish: Revolución de Mayo) was a week-long series of revolutionary events that took place from May 18 to May 25, 1810, in Buenos Aires, capital of the Viceroyalty of the Río de la Plata, a colony of the Spanish Empire which included the present-day nations of Argentina, Bolivia, Paraguay and Uruguay. The consequences of these events were the ousting of Viceroy Baltasar Hidalgo de Cisneros and the establishment of a local government, the Primera Junta (First Junta) on May 25. These events are commemorated in Argentina as "May Week" (Spanish: Semana de Mayo).

Commemorates the death of Manuel Belgrano, (1770 - 1820) an Argentine lawyer, politician, and general in the first autonomous government of Argentina who in 1812, created the national flag of Argentina. It was raised for the first time on February 27 of that year, in an island in the Parana River, opposite the city of Rosario. He also led the Jujuy Exodus (Exodo Jujeno), which prepared the ground for victories of the Argentine War of Independence in the northwest of the country. Official day of celebration is June 20.

Argentine Declaration of Independence from Spain in 1816. What today is commonly referred as the Independence of Argentina was declared on July 9, 1816 by the Congress of Tucumán. Actually, Argentina was not a country yet; the congressmen joined in Tucuman declared the independence of the United Provinces of South America (still today one of the legal names of the Argentine Republic). The three Litoral provinces (Santa Fé, Entre Ríos and Corrientes) were expelled from the Congress, along with Banda Oriental, present-day Uruguay. At the same time, several provinces from the Alto Perú were represented that would later become part of present-day Bolivia.

José Francisco de San Martín Matorras, also known as José de San Martín (25 February 1778 – 17 August 1850), was an Argentine general and the prime leader of the southern part of South America's successful struggle for independence from Spain.

Many countries in the New World and elsewhere celebrate the anniversary of Christopher Columbus's arrival in the Americas, which occurred on October 12, 1492 in the Julian calendar and October 21, 1492 in the modern Gregorian calendar, as an official holiday. The day is celebrated as Columbus Day in the United States, as Día de la Raza in many countries in the Americas, as Día de las Culturas (Day of the Cultures) in Costa Rica, as Discovery Day in the Bahamas, as Día de la Hispanidad and Fiesta Nacional in Spain and as Día de las Américas (Day of the Americas) in Uruguay. These holidays have been celebrated unofficially since the late 18th century, and officially in various countries since the early 20th century.

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