How many time differences are there in the us

Baltimore Maryland. Washington Washington, D. Milwaukee Wisconsin. South Boston Massachusetts. Albuquerque New Mexico. Tucson Arizona. Nashville Tennessee. Fresno California. Sacramento California. Kansas City Missouri. Long Beach California. Mesa Arizona. Staten Island New York. Atlanta Georgia. Colorado Springs Colorado. Virginia Beach Virginia. Raleigh North Carolina.

Omaha Nebraska. Miami Florida. Oakland California. Continent North America. States Alaska. Washington, D. North Carolina. When mechanical clocks became common in the 19th century, mean solar time was used. Apparent and mean solar time may differ by up to 15 minutes. Further advances led to the concept of standard time zones. Time zones are regions on the globe that observe the same standard time. The local time in a given time zone is defined by its offset from Coordinated Universal Time UTC , which is the primary time standard used throughout the world.

UTC time either changes backward or forward by one hour for every 15 degrees west or east of the prime meridian. By law, time in the United States US and its possessions is divided into nine standard time zones. The time zones in the contiguous US are often referred to by their generic name, without making a difference between standard time and Daylight Saving Time designations. In practice, this means that the local time in these time zones changes when DST begins and ends.

Note: Local time in these time zones changes when Daylight Saving Time begins and ends. The above time zones are used during other parts of the year. They will become active again after the next clock change as Daylight Saving Time begins or ends.

Time zones in the USA are defined in the U.