The Times Square Ball completes its descent at midnight on New Year's Eve, marking the start of the new year.
The ceremony is designed around the final sixty seconds of December 31. The illuminated ball begins descending at 11:59 p.m. Eastern Time and reaches the bottom at the instant the clock changes to 12:00 a.m. The countdown is broadcast internationally and accompanied by cheering, confetti, and fireworks or pyrotechnic effects.
Midnight is the local civil time in New York, not a universal simultaneous moment. Because time zones cross the globe, other cities welcome the new year earlier or later. The Times Square event therefore begins the American East Coast's New Year rather than the world's first New Year.