In pre-Christian Rome, under the Julian calendar, the day was dedicated to Janus, god of gateways and beginnings, for whom January is also named.

(Septem is Latin for "seven"; octo, "eight"; novem, "nine"; and decem, "ten") Roman mythology usually credits their second king Numa with the establishment of the two new months of Ianuarius and Februarius.

A series of disasters, notably including the failed rebellion of M. Aemilius Lepidus in 78 BC, established a superstition against allowing Rome's market days to fall on the kalends of January and the pontiffs employed intercalation to avoid its occurrence.

Several local provincial calendars were aligned to start on the birthday of the Emperor Augustus, 23 September.

At various times and in various places throughout mediaeval Christian Europe, the new year was celebrated on 25 December in honour of the birth of Jesus; 1 March in the old Roman style; 25 March in honour of Lady Day (the Feast of the Annunciation, the date of the conception of Jesus); and on the movable feast of Easter.

[2][4] Christians of various denominations (Catholics, Lutherans, Anglicans, and Moravians, among others) often attend a watchnight service (also known as a Watchnight Mass if Holy Communion is celebrated) on the night of New Year's Eve and this liturgy concludes in the morning of New Year's Day.

The mainstream Roman Catholic Church celebrates on this day the Solemnity of Mary, Mother of God.

This custom was deplored by Saint Eligius (died 659 or 660), who warned the Flemish and Dutch: "(Do not) make visuals, [little figures of the Old Woman], little deer or iotticos or set tables [for the house-elf, compare Puck] at night or exchange New Year gifts or supply superfluous drinks [another Yule custom].

Most of Germany changed to 1 January from 1544, the Netherlands did so from 1556 or 1573 according to sect, Spain and Portugal from 1556, France from 1564, Italy (pre-unification) on a variety of dates, Sweden, Norway and Denmark from 1599, Scotland from 1600,[23] and Russia from 1700 or 1725.

[2] England, Wales, Ireland, and Britain's American colonies adopted 1 January as New Year's Day from 1752.

[2][4] Until Tuesday, 31 December 1751[a] (except Scotland),[b] the Kingdom of Great Britain and the British Empire at the time had retained 25 March as the official start of the year, although informal use of 1 January had become common.

In cultures and religions that traditionally or currently use calendars other than the Gregorian, New Year's Day is often also an important celebration.

In many countries, New Year's Eve is celebrated with dancing, eating, drinking, and watching or lighting fireworks.

The first places to welcome the New Year are the Line Islands (part of Kiribati), Samoa and Tonga, in the Pacific Ocean.

In some cases, publications may set their entire year's work alight in the hope that the smoke emitted from the flame brings new life to the company.

On New Year's Day in Antarctica, the stake marking the geographic south pole is moved approximately 10 meters to compensate for the movement of the ice.