GMT -- Definition

GMT is  an abbreviation of  Greenwich Mean Time,  the time recorded  at the
Greenwich  Observatory in  England, where  by international  convention the
Earth's zero meridian is fixed.

By definition, COHERENT fixes system time in GMT.  It calculates local time
as an  offset of GMT; for  example, the time zone for  Chicago is six hours
(360 minutes) behind Greenwich, so the local time for Chicago is calculated
by subtracting 360 minutes from GMT.

See Also

gmtime(),
localtime,
Programming COHERENT,
time,
time.h,
TIMEZONE

Notes

The  ANSI Standard  replaces  GMT with  UTC (universel  temps coordonne  or
universal coordinated time) for C programming.  The change is mainly one of
terminology  rather than  substance, as  some signatories  to international
conventions object to naming the standard for global time after a suburb of
London.

Under international convention, there  are two UTC standards: UTC1 is based
on solar time and is identical  to current GMT; and UTC2, which uses atomic
clocks  that are  corrected by  comparison  with pulsars.   These standards
drift  apart as  the  earth's rotation  slows; thus,  ``leap seconds''  are
inserted periodically into UTC1 to bridge the difference.

© 2012 by Stephen A. Ness