Which calendar's New Year is marked by the Times Square Ball Drop on December 31?

The Times Square Ball Drop on December 31 marks the New Year of the Gregorian calendar.

The Gregorian calendar is the civil calendar used by most countries and international institutions. Its New Year begins on January 1, so the Times Square celebration starts on December 31 and reaches its climax at midnight as the date changes to January 1.

Pope Gregory XIII introduced the calendar in 1582 to correct the Julian calendar’s accumulated drift from the solar year. The Gregorian system refined the leap-year rule: century years are not leap years unless divisible by 400. Thus 2000 was a leap year, while 1900 was not.

The Gregorian calendar was adopted at different times in different countries, and some religious communities continue to use other calendars for festivals. The Times Square event is therefore a civil-calendar celebration, not a universal statement that every culture begins its year on January 1. The ball itself is a New York tradition dating to 1907.