Time synchronization in North America

Time synchronization in North America can be achieved with many different methods, some of which require only a telephone, while others require expensive, sensitive, and rare electronic equipment. In the United States, the United States Naval Observatory provides the standard of time, called UTC(USNO), for the United States military and the Global Positioning System, while the National Institute of Standards and Technology provides the standard of time for civil purposes in the United States, called UTC(NIST).
ITU-R Standard Frequency and Time Signals.
A standard frequency and time signal service is a station that operates on or immediately adjacent to 2.5 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz, and 25 MHz, as specified by "Article 5" of the ITU Radio Regulations (edition 2012)
The methods below provide either Coordinated Universal Time (UTC), which is defined by "Recommendation ITU-R TF.460", or the official U.S. implementation of UTC, officially labeled UTC (NIST).
Internet time sources.
Several different time synchronization protocols exist on the Internet, including:
GPS time synchronization.
GPS receiver requirements
Telephone time sources.
Several different organizations provide publicly accessible recorded voice time sources, including the NIST Telephone Time of Day Service, see speaking clock#United States.