<P> Time in the United States , by law , is divided into nine standard time zones covering the states and its possessions , with most of the United States observing daylight saving time ( DST ) for approximately the spring , summer , and fall months . The time zone boundaries and DST observance are regulated by the Department of Transportation . Official and highly precise timekeeping services ( clocks ) are provided by two federal agencies : the National Institute of Standards and Technology ( NIST ) ( an agency of the Department of Commerce ) ; and its military counterpart , the United States Naval Observatory ( USNO ) . The clocks run by these services are kept synchronized with each other as well as with those of other international timekeeping organizations . </P>
<P> Time in the United States , by law , is divided into nine standard time zones covering the states and its possessions , with most of the United States observing daylight saving time ( DST ) for approximately the spring , summer , and fall months . The time zone boundaries and DST observance are regulated by the Department of Transportation . Official and highly precise timekeeping services ( clocks ) are provided by two federal agencies : the National Institute of Standards and Technology ( NIST ) ( an agency of the Department of Commerce ) ; and its military counterpart , the United States Naval Observatory ( USNO ) . The clocks run by these services are kept synchronized with each other as well as with those of other international timekeeping organizations . </P>
how many time zones across the united states
how many time zones across the united states
nine
nine