Other US time zones follow the same format and moving westward, each time zone adds an additional 1-hour offset. Eastern Daylight Time (EDT), which is used during spring/summer and is four hours behind UTC.Eastern Standard Time (EST), which is used during autumn/winter and is five hours behind UTC.The time zone on the east coast is called Eastern Time (ET), divided into: two time zones beyond the contiguous USA.The United States observes 9 time zones as below: Publications 8" x 10", 192 pages Table of Contents.Like all time zones worldwide, the time zones for the USA are based on UTC (Coordinated Universal Time, formerly GMT, Greenwich Mean Time - originally based on London, UK). This calendar has become a standard in such worldwide industries as aviation, and international commerce and trade - however, other calendars do exist. The United States and many other countries use the Christian Gregorian calendar to mark years. United States ANSI X3.30 and NIST FIPS 4-1, The date format Year-Month-Day has become widely accepted as a standard in many countries. Virtually the entire world formats time as Hours:Minutes:Seconds (hours listed before minutes, minutes listed before seconds). REFERENCE: A Briefer History of Time - Howard Barnes, Georgi Dobrovolski Solar Observatory, New Zealand, 2010. UTC - civil atomic time scale on or about the Greenwich meridian kept within 0.9 seconds of UT1.UT2 - UT1 corrected for seasonal variation in the Earth's rotation (a smoothed scale that does not reflect the real periodic variations in the Earth's angular position).UT1 - UT0 corrected for polar motion (widely used).The time 00 hours being at Greenwich mean midnight. UT0 - mean solar time on the Greenwich meridian obtained from direct astronomical observation.UT - An abbreviation (for Universal Time) that should be used to show approximation of all the below.second - One second (1 s or 1 sec.) is the duration of 9,192,631,770 periods of radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom (Cs).Mean solar time - a measurement of the Earth's rotation with respect to the 'fictitious' mean sun.Atomic clock - usually multiple clocks that count seconds (average of all clocks in system) based on the frequency of the cesium 133 atom (Cs) which oscillates at 9,192,631,770 Hertz.DST was never practical and will eventually be phased out (obsolete). There is no consistency between regions as to when DST takes affect, or reverts back to standard (real) time. Time Zone Chart (PDF file) 8.5 x 14 inches, 240 kB, colorĭaylight savings time (DST) is used in the summer months in some regions. Twenty four hour time does not use "am" or "pm", but courts hours from midnight (0 hours) to 11 pm (23 hours). ![]() ![]() Daylight savings time adds 1 hour to the local standard (real) time. Time in other locations will be the UTC time hour plus or minus the local Time Zone. UTC time is the local time at Greenwich England. Greenwich England is, by definition, in the middle of Time Zone 0, the prime meridian. Each time zone is 1 hour long, or 15° wide in longitude. The earth is divided into 24 time zones, -11 to +12. GMT was established by international conference in 1884 as International Time. UTC is commonly referred to as International Time, Universal Time (UT), Zulu Time (U.S. Local time is based on time zone and Coordinated Universal Time (UTC). Coordinated Universal Time (UTC) Home Coordinated Universal Time
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