The Julian calendar, 1 by Julius Caesar in 46 BC, made January 1 the first day of the year. But as Christianity 2 throughout Europe, efforts were made to Christianize the calendar by moving New Year's Day to dates of greater theological 3, such as Christmas or Easter. Some countries continued to use January 1. As a 4, by the 1500s the European calendar system was a mess. Not only had errors in the Julian calendar caused the solar year to diverge from the calendar year, but also countries were beginning the year on different dates. a
In 1563 King Charles IX declared January 1 to be the first day of the year. This was passed into 5 by the French Parliament on Dec. 22, 1564.