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).

Eid ul-Fitr (Arabic: عيد الفطر ‘Īdu l-Fiṭr‎), often abbreviated to Eid, is a Muslim holiday that marks the end of Ramadan, the Islamic holy month of fasting. Eid is an Arabic word meaning "festivity", while Fiṭr means "to break fast"; and so the holiday symbolizes the breaking of the fasting period. It is celebrated after the end of the Islamic month of Ramadan, on the first day of Shawwal. Eid ul-Fitr lasts for three days of celebration and is sometimes also known as the "Smaller Eid" (Arabic: العيد الصغير al-‘īdu ṣ-ṣaghīr‎) as compared to the Eid ul-Adha that lasts four days and is called the "Greater Eid" (Arabic: العيد الكبير al-‘īdu l-kabīr‎). Muslims are commanded by the Quran to complete their fast on the last day of Ramadan and then recite the Takbir all throughout the period of Eid.

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.

Eid al-Adha (Arabic: عيد الأضحى‎ ‘Īdu l-’Aḍḥā) "Festival of Sacrifice" or "Greater Eid" is an important religious holiday celebrated by Muslims worldwide to commemorate the willingness of Abraham (Ibrahim) to sacrifice his son as an act of obedience to God, but instead was able to sacrifice a ram (by God's command). Eid is also about spending time with family and friends, sacrifice, and thanksgiving for being able to afford food and housing. In traditional or agrarian settings, each family would sacrifice a domestic animal, such as a sheep, goat, cow, or camel, by slaughter (though many contemporary muslims do not sacrifice an animal as part of their observance). The meat would then be divided into three equal parts to be distributed to others. The family eats one third, another third is given to other relatives, friends or neighbors, and the other third is given to the poor as a gift. Eid al-Adha is the latter of two Eid festivals celebrated by Muslims, whose basis comes from the Quran. Like Eid ul-Fitr, Eid al-Adha begins with a short prayer followed by a sermon (khuṭba). Eid al-Adha is celebrated annually on the 10th day of the month of Dhul Hijja (ذو الحجة) of the lunar Islamic calendar. The festivities last for three days or more depending on the country. Eid al-Adha celebrations start after the Hajj, the annual pilgrimage to Mecca in Saudi Arabia by Muslims worldwide, descend from Mount Arafat. The date is approximately 70 days after the end of the month of Ramadan.

Mawlid (Eid Milad an-Nabi) (Qur'anic Arabic: مَوْلِدُ آلنَبِيِّ‎ mawlidu n-nabiyyi, “Birth of the Prophet” Standard Arabic: مولد النبي mawlid an-nabī, sometimes simply called in colloquial Arabic مولد , mawlid, múlid, mulud, milad among other vernacular pronunciations) is a term used to refer to the observance of the birthday of the Islamic prophet Muhammad which occurs in Rabi' al-awwal, the third month in the Islamic calendar. The term Mawlid is also used in some parts of the world, such as Egypt, as a generic term for the birthday celebrations of other historical religious figures such as Sufi saints. Where Mawlid is celebrated in a carnival manner, large street processions are held and homes or mosques are decorated. Charity and food is distributed, and stories about the life of Muhammad are narrated with recitation of poetry by children. Scholars and poets celebrate by reciting Qaṣīda al-Burda Sharif, the famous poem by 13th century Arabic Sufi Busiri. Mawlid is celebrated in most Muslim countries, and in other countries where Muslims have a presence, such as India, Britain, and Canada. Saudi Arabia is the only Muslim country where Mawlid is not an official public holiday. Participation in the ritual celebration of popular Islamic holidays is seen as an expression of the Islamic revival. Among non-Muslim countries, India is noted for its Mawlid festivities. The relics of Muhammed are displayed after the morning prayers in the Indian states of Jammu and Kashmir at Hazratbal shrine, on the outskirts of Srinagar. Shab-khawani night-long prayers held at the Hazratbal shrine are attended by thousands. During Pakistan's Mawlid celebration, the national flag is hoisted on all public buildings, and a 31 gun salute in the federal capital and a 21 gun salute at the provincial headquarters are fired at dawn. The cinemas shows religious rather than secular films on 11th and 12th Rabi-ul-Awwal.

In Islamic tradition, the Night Journey, Isra and Mi'raj (Arabic: الإسراء والمعراج‎, al-’Isrā’ wal-Mi‘rāğ), are the two parts of a journey that the Islamic prophet Muhammad took in one night, around the year 621. Many Muslims consider it a physical journey but some scholars consider it a dream or vision. A brief sketch of the story is in verses 1 and 60 of one of the Qur'an chapters (#17: sura Al-Isra), and other details were filled in from the supplemental writings, the hadith. The event is celebrated each year via a festival for families, the Lailat al Miraj, one of the most important events in the Islamic calendar. Muslims bring their children to the mosques, where the children are told the story, pray with the adults, and then afterwards food and treats are served.