The Times Square Ball drop is synchronized using a time signal from the U.S. National Institute of Standards and Technology (NIST).
The ball descends from One Times Square during the final minute of December 31. Its control system uses a precise NIST time signal received by satellite, allowing the descent to finish exactly at midnight Eastern Time. NIST is the federal agency responsible for maintaining the United States’ official time standards.
The modern drop grew from an earlier New York Times publicity event. The first ball descended on December 31, 1907, welcoming 1908, after fireworks had been used at the newspaper’s headquarters. The ball itself was inspired by maritime time balls, which once signaled precise time to ships and nearby observers.
A common mix-up is confusing NIST with NASA, NOAA, or the FCC. Those agencies have important scientific or communications roles, but NIST is the agency associated with the official timing signal used for the drop.