Coordinated Universal Time (UTC)*

Hours behind (-), or ahead of, UT
UTC Zones

Coordinated Universal Time (UTC), also referred to as Zulu Time by the U.S. military, and mistakenly (due to different measuring methodologies that result in differences on the order of a second) referred to as Greenwich Mean Time (GMT) (recognized by international conference in 1884), is the time at the prime meridian (0° ±7.5° longitude), and used by numerous agencies worldwide. Each time zone is 15° wide (1 hour). The International Date Line is on the other side of the world (in the middle of the 12th UTC zone) at 180° longitude.

NOTE: The word order of Coordinated Universal Time versus the UTC abbreviation (out of order) is intentional -- established by the Bureau International de l'Heure (International Time Bureau) as a language-independent abbreviation.

UTC is;
equal to time at longitude 0° ± 7.5°,
equal to time in Greenwich, England,
5 hours ahead of EST (CDT),
6 hours ahead of CST (MDT),
7 hours ahead of MST (PDT),
8 hours ahead of PST.

EST- Eastern Standard Time, CDT- Central Daylight savings Time,
CST- Central Standard Time, MDT- Mountain Daylight savings Time,
MST- Mountain Standard Time, PDT- Pacific Daylight savings Time,
PST- Pacific Standard Time.

Below list local times (in am/pm and 24 hour time) for the 4 time zones in the continental United States versus UTC. Note, 24 hour time refers to midnight as 00:00 hours or 24:00 hours.

COORDINATED    Eastern        Central         Mountain        Pacific     
 UNIVERSAL     Standard       Standard        Standard        Standard   
 TIME (UTC)    Time (EST)     Time (CST)      Time (MST)      Time (PST)

 MIDNIGHT     7pm, 19:00      6pm, 18:00      5pm, 17:00      4pm, 16:00
   01:00      8pm, 20:00      7pm, 19:00      6pm, 18:00      5pm, 17:00
   02:00      9pm, 21:00      8pm, 20:00      7pm, 19:00      6pm, 18:00
   03:00     10pm, 22:00      9pm, 21:00      8pm, 20:00      7pm, 19:00
   04:00     11pm, 23:00     10pm, 22:00      9pm, 21:00      8pm, 20:00
   05:00       MIDNIGHT      11pm, 23:00     10pm, 22:00      9pm, 21:00
   06:00      1am, 01:00       MIDNIGHT      11pm, 23:00     10pm, 22:00
   07:00      2am, 02:00      1am, 01:00       MIDNIGHT      11pm, 23:00
   08:00      3am, 03:00      2am, 02:00      1am, 01:00       MIDNIGHT
   09:00      4am, 04:00      3am, 03:00      2am, 02:00      1am, 01:00
   10:00      5am, 05:00      4am, 04:00      3am, 03:00      2am, 02:00
   11:00      6am, 06:00      5am, 05:00      4am, 04:00      3am, 03:00
NOON 12:00    7am, 07:00      6am, 06:00      5am, 05:00      4am, 04:00
   13:00      8am, 08:00      7am, 07:00      6am, 06:00      5am, 05:00
   14:00      9am, 09:00      8am, 08:00      7am, 07:00      6am, 06:00
   15:00     10am, 10:00      9am, 09:00      8am, 08:00      7am, 07:00
   16:00     11am, 11:00     10am, 10:00      9am, 09:00      8am, 08:00
   17:00     NOON  12:00     11am, 11:00     10am, 10:00      9am, 09:00
   18:00      1pm, 13:00     NOON  12:00     11am, 11:00     10am, 10:00
   19:00      2pm, 14:00      1pm, 13:00     NOON  12:00     11am, 11:00
   20:00      3pm, 15:00      2pm, 14:00      1pm, 13:00     NOON  12:00
   21:00      4pm, 16:00      3pm, 15:00      2pm, 14:00      1pm, 13:00
   22:00      5pm, 17:00      4pm, 16:00      3pm, 15:00      2pm, 14:00
   23:00      6pm, 18:00      5pm, 17:00      4pm, 16:00      3pm, 15:00

DEFININTIONS

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.

Mean solar time -- a measurement of the Earth's rotation with respect to the 'fictitious' mean sun.

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).

UT -- An abbreviation (for Universal Time) that should be used to show approximation of all the below.

UT0 -- mean solar time on the Greenwich meridian obtained from direct astronomical observation. The time 00 hours being at Greenwich mean midnight.

UT1 -- UT0 corrected for polar motion (widely used).

UT2 -- UT1 corrected for seasonal variation in the Earth's rotation (a smoothed scale that does not reflect the real periodic variatios in the Earth's angular position).

UTC -- civil atomic time scale on or about the Greenwich meridian kept within 0.9 seconds of UT1.

Standard Date Format

Virtually the entire world formats time as Hours:Minutes:Seconds (hours listed before minutes, minutes listed before seconds). The date format Year-Month-Day has become widely accepted as a standard in many countries.

International Standard ISO 8601
United States ANSI X3.30 and NIST FIPS 4-1 standards
Canadian standard CSA Z234.5
European standard EN 28601
British standard BS EN 28601

ISO 8601 FORMAT    EXAMPLEs

           year    2001
     year-month    2001-04       2001-April
 year-month-day    2001-04-18    2001 April 18    20010418

Year 2000

The United States and many other countries use the Christian (Gregorian) calendar to mark years. This calendar has become a standard in such worldwide industries as aviation, and international commerce and trade -- however, other calendars do exist.

       CALANDER    YEAR

         Jewish    5760-5761
        Chinese    4698 (Year of the Dragon)
      Old Roman    2753
       Buddhist    2544
      Christian    2000
         Coptic    1716
        Islamic    1420-1421

Police Traffic Radar Handbook
Coordinated Universal Time (UTC)