Celebrating Nowruz, a haftseen table has seven items – each begins with a Persian letter “s” and is a symbol of rebirth and renewal. [Photo: creativeelixir/Getty Images/iStockphoto]

Imagine midnight on December 31 – fireworks, friendship and celebration greet a new year. But only if you follow the Gregorian calendar. In the past, a year often didn't start on January 1, and for nearly two billion people it still doesn't. So when does a new year begin?

Akitu
The oldest New Year records are around 4000 years old. They refer to the Babylonian festival of Akitu. If you'd lived then, your year would have begun in the spring at the first new moon after the spring equinox. Akitu prepared the people spiritually for the rebirth of the natural world.

Nowruz (Persian new year)
For some 300 million people in Iran and elsewhere in the Middle East and Asia, the New Year still begins at the spring equinox. People are gathered as the Sun crosses the celestial equator. Nowruz is a 13-day festival whose origins go back over two thousand years. Traditions include special foods, bonfires, dyeing eggs, exchanging presents and meeting with family and friends.

Chinese New Year
In China and places with a significant Chinese population, over a billion people celebrate the New Year. There's a lively and noisy side to the festivities, and the Chinese were the first to add fireworks to the celebration. (This was back in the tenth century.)

China has a lunisolar calendar that takes account of Moon cycles as well as the solar year. Like Nowruz, Chinese New Year is a spring festival, but it's not based on the vernal equinox. The second new moon after the winter solstice signals the start of spring, which puts it in late January or early February.

Wepet Renpet
In ancient Egypt the New Year began in mid-Summer. The sign wasn't the Sun or the Moon, but rather the bright star Sirius. In early May Sirius dropped below the horizon. When it reappeared in mid-July the Egyptians celebrated Wepet Renpet (“opening of the year”). The significance of the star's reappearance was that it was near the time of the life-giving Nile floods that kept their farmlands fertile.

Julian calendar
Lunar calendars get messy because there aren't a whole number of Moon cycles in a year. They need adjustments to keep you from finding yourself, say, celebrating a harvest festival in mid Winter. Julius Caesar had the Roman lunar calendar reformed into a solar calendar. Since there also isn't a whole number of days in a year, the Julian calendar provided for leap years to keep it in synch with the seasons. Although the Roman year had previously begun at the spring equinox, Julius decreed that the year would start on January 1st.

January 1st abolished as New Year's Day
Centuries of people having a good time on New Year's Eve was too much for the Church. In 567 the Council of Tours declared January 1, with its pagan and unchristian behavior, wouldn't mark the year's start. It was to begin on more sober holy days.

The result was that over the next thousand years or so, in different places and times there were variations in the start of the year. Spring beginnings were the most common. For several centuries many European countries took the Saturday before Easter as the date of the New Year. In England, the Annunciation on March 25th marked the start of the year until 1752 when they adopted the Gregorian calendar.

January 1st reinstated
Pope Gregory XIII reformed the Julian calendar in 1582. Due to a miscalculation in the insertion of leap days, it was getting increasingly out of synch with the solar year. The Gregorian calendar tidied that up and restored January 1 as New Year's Day.

Although Roman Catholic countries adopted the new calendar fairly quickly, there was a lot of back-pedaling elsewhere. The last European country to adopt it was Greece – 341 years later.

By now, most of the world uses the Gregorian calendar for civil and commercial purposes. But the Chinese and the Iranians aren't the only ones who have also kept their own calendars. Some Orthodox Christian churches still use the old Julian calendar for liturgical purposes, so their January 1 corresponds to a later date on the Gregorian calendar.

Islamic New Year and Jewish New Year
The Islamic calendar is a lunar calendar with 354 days, so holidays migrate through the seasons. The year begins on the first day of Muharram, but that's fixed only within the Islamic calendar. For example, from 2008-2017 the Islamic New Year occurred as early as October 3rd and as late as December 29th on the Gregorian calendar.

Islamic New Year is a quiet affair. In remembrance of the Prophet Muhammad fleeing an assassination plot in Mecca, the day is often one for fasting, worship and reflection.

The Jewish calendar is a lunisolar calendar, and the new year – Rosh Hashanah – occurs on the first day of the first month of the civil year. That usually falls in September or early October. There's a festive side to the celebration with centuries of tradition behind it, but it's also a time for prayer and personal introspection.

Enqutatash
Ethiopia has its own unique calendar based on what's known as a Coptic calendar. Enqutatash is celebrated on September 11, the end of the rainy season that leaves the countryside in bloom. It's both a religious and secular celebration of change, thanksgiving and renewal.

Revolutionary France
Let's end our exploration with an oddity, the Republican Calendar in use from 1793-1805 and in the 1871 Paris Commune. It was unusual in having the year begin at the autumn equinox.