The New Year is the time or day at which a new calendar year begins and the calendar's year count increments by one. Many cultures celebrate the event in some manner. In the Gregorian calendar, the most widely used calendar system today, New Year occurs on January 1 (New Year's Day, preceded by New Year's Eve). This was also the first day of the year in the original Julian calendar and the Roman calendar (after 153 BC).
Other cultures begin their traditional or religious year according to their own customs – typically (though not invariably) because they use a lunar calendar or a lunisolar calendar: the lunisolar Chinese calendar (and its variants), the lunar Islamic calendar and the lunisolar Hebrew calendar are among well-known examples. The Iranian calendar begins the year at the March equinox; the Ethiopian calendar begins in (Gregorian) September. India has many traditional calendars with a matching variety of first days. There are many more traditional calendars with associated start days: these are listed below.
During the Middle Ages in Western Europe, while the Julian calendar was still in use, authorities moved New Year's Day, depending upon locale, to one of several other days, including March 1, March 25, Easter, September 1, and December 25. Since then, many national civil calendars in the Western World and beyond have changed to using one fixed date for New Year's Day, January 1—most doing so when they adopted the Gregorian calendar.

By type
Based on the used calendar new years are often categorized between lunar or lunisolar new years or solar new years.
By month or season
January
January 1: The first day of the civil year in the Gregorian calendar used by most countries.
Contrary to common belief in the west, the civil New Year of January 1 is not an Orthodox Christian religious holiday. The Eastern Orthodox liturgical calendar makes no provision for the observance of a New Year. January 1 is itself a religious holiday, but that is because it is the feast of the Circumcision of Jesus (seven days after his birth), and a commemoration of saints. While the liturgical calendar begins September 1, there is also no particular religious observance attached to the start of the new cycle. Orthodox nations may, however, make civil celebrations for the New Year. Those who adhere to the revised Julian calendar (which synchronizes dates with the Gregorian calendar), including Bulgaria, Cyprus, Egypt, Greece, Romania, Syria, Turkey and Ukraine, observe both the religious and civil holidays on January 1. In other nations and locations where Orthodox churches still adhere to the Julian calendar, including Georgia, Israel, Russia, North Macedonia, Serbia, Montenegro and Russian-occupied Ukraine, the civil new year is observed on January 1 of the civil calendar, while those same religious feasts occur on January 14 Gregorian (which is January 1 Julian), in accord with the liturgical calendar.

The Japanese New Year (正月, Shōgatsu) is currently celebrated on January 1, with the holiday usually being observed until January 3, while other sources say that Shōgatsu lasts until January 6. In 1873, five years after the Meiji Restoration, Japan adopted the Gregorian calendar. Prior to 1873, Japan used a lunar calendar with twelve months each of 29 or 30 days for a total year of about 354 days.
The Sámi celebrated Ođđajagemánnu.
Winter lunisolar new years
Lunisolar calendars count months according to lunations but, because there are not an even number of lunar cycles in a solar year, the calendar must be restarted annually on the first, second or even third new moon after the winter solstice. (The term "lunar calendar" is often used of lunisolar calendars, but true lunar calendars (such as the Islamic calendar) count only lunations and ignore the solar seasons.)

The Chinese New Year, also known as Spring Festival or Lunar New Year, occurs every year on the new moon of the first lunar month, about the beginning of spring (Lichun). The exact date can fall any time between January 21 and February 21 (inclusive) of the Gregorian Calendar. Traditionally, years were marked by one of twelve Earthly Branches, represented by an animal, and one of ten Heavenly Stems, which correspond to the five elements. This combination cycles every 60 years. It is the most important Chinese celebration of the year.
The Korean New Year is a Seollal or Lunar New Year's Day. Although January 1 is, in fact, the first day of the year, Seollal, the first day of the lunar calendar, is more meaningful for Koreans. A celebration of the Lunar New Year is believed to have started to let in good luck and ward off bad spirits all throughout the year. With the old year out and a new one in, people gather at home and sit around with their families and relatives, catching up on what they have been doing.
The Vietnamese New Year is the Tết Nguyên Đán which most times is the same day as the Chinese New Year due to the Vietnamese using a lunisolar calendar similar to the Chinese calendar.

The Tibetan New Year is Losar and falls between January and March.
The Taiwanese New Year is called Kuè-nî and falls between January and March.
March
Babylonian New Year began with the first New Moon after the northward equinox. Ancient celebrations lasted for eleven days.

Nava Varsha is celebrated in India in various regions from March–April.
The Iranian New Year, called Nowruz, is the day containing the exact moment of the Northward equinox, which usually occurs on March 20 or 21, marking the start of the spring season. The Zoroastrian New Year coincides with the Iranian New Year of Nowruz and is celebrated by the Parsis in India and by Zoroastrians and Persians across the world. In the Baháʼí calendar, the new year occurs on the vernal equinox on March 20 or 21 and is called Naw-Rúz. The Iranian tradition was also passed on to Central Asian countries, including Kazakhs, Uzbeks, and Uighurs, and there is known as Nauryz. It is usually celebrated on March 22.
The Balinese New Year, based on the Saka Calendar (Balinese-Javanese Calendar), is called Nyepi, and it falls on Bali's Lunar New Year (around March). It is a day of silence, fasting, and meditation: observed from 6 am until 6 am the next morning, Nyepi is a day reserved for self-reflection and as such, anything that might interfere with that purpose is restricted. Although Nyepi is a primarily Hindu holiday, non-Hindu residents of Bali observe the day of silence as well, out of respect for their fellow citizens. Even tourists are not exempt; although free to do as they wish inside their hotels, no one is allowed onto the beaches or streets, and the only airport in Bali remains closed for the entire day. The only exceptions granted are for emergency vehicles carrying those with life-threatening conditions and women about to give birth.
Ugadi (Telugu: ఉగాది, Kannada: ಯುಗಾದಿ); the Telugu and Kannada New Year, generally falls in the months of March or April. The people of Andhra Pradesh, Telangana and Karnataka states in southern India celebrate the advent of New Year's Day in these months. The first month of the new year is Chaitra Masa.
In the Kashmiri calendar, the holiday Navreh marks the New Year in March–April. This holy day of Kashmiri Brahmins has been celebrated for several millennia.
Gudi Padwa is celebrated as the first day of the Hindu year by the people of Maharashtra, India and Sanskar Padwa is celebrated in Goa. This day falls in March–April and coincides with Ugadi. (see: Deccan)
The Sindhi festival of Cheti Chand is celebrated on the same day as Ugadi/Gudi Padwa to mark the celebration of the Sindhi New Year.
The Thelemic New Year on March 20 (or on April 8 by some accounts) is usually celebrated with an invocation to Ra-Hoor-Khuit, commemorating the beginning of the New Aeon in 1904. It also marks the start of the twenty-two-day Thelemic holy season, which ends on the third day of the writing of The Book of the Law. This date is also known as The Feast of the Supreme Ritual. There are some that believe the Thelemic New Year falls on either March 19, 20, or 21, depending on the vernal equinox, which is The Feast for the Equinox of the Gods on the vernal equinox of each year to commemorate the founding of Thelema in 1904. In 1904 the vernal equinox was on March 21, and it was the day after Aleister Crowley ended his Horus Invocation that brought on the new Æon and Thelemic New Year.
From 1155 until 1752, the civil year in England and its possessions began on March 25 (see below.)
April
The Assyrian-Babylonian New Year, called Kha b'Nissan or Resha d'Sheeta, occurs on April 1.
Thelemic New Year Celebrations usually end on April 10, after an approximately one-month-long period that begins on March 20 (the formal New Year). This one-month period is referred to by many as the High Holy Days, and end with periods of observance on April 8, 9, and 10, coinciding with the three days of the Writing of the Book of the Law by Aleister Crowley in 1904.
Mid-April (Spring in the Northern Hemisphere)
The new year of many South and Southeast Asian calendars falls between April 13–15, marking the beginning of spring.
The Baloch Hindu people in Pakistan and India celebrate their new year called Bege Roch in the month of Daardans according to their Saaldar calendar.
Tamil New Year (Tamil: தமிழ்புத்தாண்டு Puthandu) is celebrated in the South Indian state of Tamil Nadu, on the first of Chithrai (சித்திரை) (April 13, 14, or 15). In the temple city of Madurai, the Chithrai Thiruvizha is celebrated in the Meenakshi Temple. A huge exhibition is also held, called Chithrai Porutkaatchi. In some parts of Southern Tamil Nadu, it is also called Chithrai Vishu. The day is marked with a feast in Hindu homes and the entrance to the houses are decorated elaborately with kolams.
Punjabi/Sikh Vaisakhi (ਵਿਸਾਖੀ) is celebrated on April 14 in Punjab according to their nanakshahi calendar.
Nepal New Year in Nepal is celebrated on the 1st of Baisakh Baisākh which falls on 12–15 April in the Gregorian calendar. Nepal follows the Bikram Sambat (BS) as an official calendar.
The Dogra of Himachal Pradesh celebrate their new year Chaitti in the month of Chaitra.
Maithili New Year or Jude-Sheetal too fall on these days. It is celebrated by Maithili People all around the world.
Assamese New Year (Rongali Bihu or Bohag Bihu) is celebrated on April 14 or 15 in the Indian state of Assam.
Bengali New Year (Bengali: পহেলা বৈশাখ Pôhela Boishakh or Bengali: বাংলা নববর্ষ Bangla Nôbobôrsho) is celebrated on the 1st of Boishakh (April 14 or 15) in Bangladesh and the Indian states of West Bengal, Tripura, Barak Valley of Assam, Jharkhand and Andaman and Nicobar Islands.
Odia New Year (Vishuva Sankranti) is celebrated on April 14 in the Indian state of Odisha. It is also called Vishuva Sankranti or Pana Sankranti (ପଣା ସଂକ୍ରାନ୍ତି).
Manipuri New Year or Cheirouba is celebrated on April 14 in the Indian State of Manipur with much festivities and feasting.
Sinhalese New Year is celebrated with the harvest festival (in the month of Bak) when the sun moves from the Meena Rashiya (House of Pisces) to the Mesha Rashiya (House of Aries). Sri Lankans begin celebrating their National New Year "Aluth Avurudda (අලුත් අවුරුද්ද)" in Sinhala and "Puththandu (புத்தாண்டு)" in Tamil. However, unlike the usual practice where the new year begins at midnight, the National New Year begins at the time determined by the astrologers by calculating the exact time that sun goes from Meena Rashiya (House of Pisces) to the Mesha Rashiya (House of Aries). Not only the beginning of the new year but the conclusion of the old year is also specified by the astrologers. And unlike the customary ending and beginning of the new year, there is a period of a few hours in between the conclusion of the Old Year and the commencement of the New Year, which is called the "nona gathe" (neutral period) Where part of the sun in House of Pisces and Part is in House of Aries.
Malayali New Year (Malayalam: വിഷു, Vishu) is celebrated in the South Indian state of Kerala in mid-April.
Western parts of Karnataka where Tulu is spoken, the new year is celebrated along with Tamil/ Malayali New year April 14 or 15, although in other parts most commonly celebrated on the day of Gudi Padwa, the Maharashtrian new year. In Kodagu, in Southwestern Karnataka, however, both new year, Yugadi (corresponding to Gudi Padwa in March) and Bisu (corresponding to Vishu in around April 14 or 15), are observed.
The Water Festival is the form of similar new year celebrations taking place in many Southeast Asian countries, on the day of the full moon of the 11th month on the lunisolar calendar each year. The date of the festival is based on the traditional lunisolar calendar which determines the dates of Buddhist festivals and holidays, and is observed from April 13 to 15. Traditionally people gently sprinkled water on one another as a sign of respect, but since the new year falls during the hottest month in Southeast Asia, many people end up dousing strangers and passersby in vehicles in boisterous celebration. The festival has many different names specific to each country:
In Burma it is known as Thingyan (Burmese: သင်္ကြန်, MLCTS: sangkran)
Songkran (Thai: สงกรานต์) in Thailand
Pi Mai Lao (Lao: ສົງກຣານ Songkan) in Laos
Chaul Chnam Thmey (Khmer: បុណ្យចូលឆ្នាំថ្មី ) in Cambodia.
It is also the traditional new year of the Dai peoples of Yunnan Province, China. Religious activities in the tradition of Theravada Buddhism are also carried out, a tradition in which all of these cultures share.
June
The New Year of the Kutchi people occurs on Ashadi Beej, that is 2nd day of Shukla paksha of Aashaadha month of Hindu calendar. As for people of Kutch, this day is associated with the beginning of rains in Kutch, which is largely a desert area. Hindu calendar month of Aashaadh usually begins on June 22 and ending on July 22.
Odunde Festival is a celebration on the 2nd Sunday of June, where "Odunde" means "Happy New Year" in the Yorube Nigerian language.
The Xooy ceremony of the Serer people of Senegal, Gambia and Mauritania marks the Serer New Year.
In the Dogon religion, the Bulo festival marks the Dogon New Year.
July
The New Year of the Zulu people occurs on the full moon of July.