Why does the New Year start on January 1?

Several countries around the world have already entered 2025, while in other nations, January 1, the first day of the year, will begin the moment the clock strikes midnight under the local time zone.

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But why does the New Year begin on January 1?

Britannica states that during his reign (c. 715-673 BCE), Roman emperor Numa Pompilius revised the Roman republican calendar to make January the year's first month instead of March. While January got its name from Janus, the Roman god of all beginnings, March was named after Mars, the god of war.

Some sources also credit Numa with the creation of January, as per the website.

Also Read: Who celebrates New Year first, who rings it in last? Country-wise details here

In 46 BCE, Julius Caesar, Rome's then king, made further changes to the calendar, but retained January 1 as the first day of the year. As the Roman empire expanded, so did the calendar, which also became known as the Julian calendar. However, after Rome fell in the 5th century CE, several Christian countries modified the calendar to make it more reflective of their religion, leading to March 25 (the Feast of the Annunciation) and December 25 (Christmas) becoming common New Year's Days.

Then, in 1582, Pope Gregory XIII brought a revised calendar. This was because the Julian one required additional changes due to a miscalculation in leap years, an error which resulted in various events occurring in the wrong season.

The Gregorian calendar, which restored January 1 as the New Year's Day, was immediately adopted by Italy, France, Spain and a few other nations. Great Britain and its American colonies did not follow the Gregorian calendar until 1753; there, March 25 was the New Year's Day.

Over time, non-Christian states also began following the Gregorian calendar.