time zone

   1. a unit representing the difference in time between a given location and Universal Time. Under ISO 8601 (see previous entry), the difference is positive if the local time is later than Universal Time and negative if it is earlier; this means that time zones are generally positive in the Eastern Hemisphere and negative in the Western Hemisphere. U.S. Eastern Standard Time is time zone -05, while Pacific Standard Time is time zone -08. For some areas, the difference between local time and Universal Time is not an exact number of hours; these time zones are specified by giving the time difference in hours and minutes. For example, Newfoundland Standard Time is time zone -03:30 or -0330. The time zone is added after a time: for example, 13:23-08 represents 1:23 pm U.S. Pacific Standard Time and is equivalent to 21:23 Universal Time. The same instant is 22:23 in Central European Time, represented by 22:23+01. The traditional acronyms for time zones, such as EST for Eastern Standard Time, may be confusing or meaningless, especially outside their country of origin, so they should not be used in international communications. Worldtimezone.com has up-to-the-moment time and time zone information for the entire world.

   2. an informal unit used to express differences in longitude between two places on the Earth. On the average, a time zone spans 15° of longitude. Of course, actual time zones have irregular boundaries, so this is only approximate. At the latitudes of the continental U.S., time zones average about 800 miles wide.