Throughout the centuries the first day of the year has moved around. The Roman empire named the first month after Janus the god of beginnings. Effectively using January 1st as the beginning of the year. This lasted until the Roman fall in the fifth century. At which point the Catholic Church changed the dates to fit with their beliefs. They still used the general outline of the Julian Calendar only had the first of the year starting on March 25th.
The Julian calendar lasted another millennium until Pope Gregory XIII created the Gregorian calendar in 1582. He restored January 1st as the beginning of the new year. While some mainly CAtholic countries immediately used his calendar, other countries used different calendars. Great Britain, including the American Colonies, kept the beginning of the year on March 25th until they adopted the Gregorian Calendar in 1752.
Other countries eventually followed suit in adopting the Gregorian Calendar. Some, like China, use the common calendar as well as their own lunar calendar. Now, most people only use the Gregorian calendar.