In message <199610032320.QAA04986@shade.twinsun.com>, Paul Eggert wrote:
That's a good suggestion for Etc/UTC and Etc/Universal, since anybody who chooses those zones probably wants `UTC'. (Also, Etc/UCT should probably generate `UCT' instead of the current `GMT'.)
What is UCT supposed to mean and why is it defined there? I have never heard this term before. Is it supposed to be "Universal Coordinated Time"??? Two alternative original abbreviation proposals were CUT (English: Coordinated Universal Time) and TUC (francais: temps universel coordine), but UTC was selected both as a compromise between the French and English proposals and because the C at the end looks more like an index in UT0, UT1, UT2 and a mathematical style notation is always the most international approach. See also <URL:http://www.boulder.nist.gov/timefreq/faq/faq.htm>: Why is the abbreviation for Coordinated Universal Time "UTC" instead of "CUT"? In 1970 the Coordinated Universal Time system was devised by an international advisory group of technical experts within the International Telecommunication Union (ITU). The ITU felt it was best to designate a single abbreviation for use in all languages in order to minimize confusion. Since unanimous agreement could not be achieved on using either the English word order, CUT, or the French word order, TUC, a compromise of using neither, UTC, was adopted. Is Coordinated Universal Time (UTC) the same thing as Greenwich Mean Time (GMT)? Greenwich Mean Time (GMT) is a 24 hour astronomical time system based on the local time at Greenwich, England. GMT can be considered equivalent to Coordinated Universal Time (UTC) when fractions of a second are not important. However, by international agreement, the term UTC is recommended for all general timekeeping applications, and use of the term GMT is discouraged.
As far as I know, GMT hasn't been an official reference time since the 1920s.
Yes, I have seen various references to some IAU conference in 1928 where an agreement was reached that the term Univeral Time (UT) shall be used, and this term has since then indeed be used quite consistently in the astronomical literature. I have never read GMT in any recent paper in "Astronomy and Astrophysics", only UT (especially when second precision is not relevant), or UTC/UT1/etc. if subsecond precision is relevant.
From <URL:http://community.bellcore.com/mbr/gmt-explained.html>:
In 1928, the International Astronomical Union recommended that the time used in the compilation of astronomical almanacs, essentially GMT, or what was also sometimes called Greenwich Civil Time, be referred to as Universal Time. The terms "Universal Time" and "Universal Day" were introduced at the various conferences in the 1800's held to set up the standard time system.
Even though the reference standard has changed a few times since then, the public continues to call it `GMT'.
I feel, GMT is only widely known in English speaking countries. In Germany for instance, the term Weltzeit (translates as "world time" or may be "universal time") is usualy used (for example on shortwave radio, Deutsche Welle ~6.1 MHz) and the time zone map that you'll find in geography school books and for example in the information booklets in every Lufthansa plane say UTC and not GMT. BTW: Quite a number of on-line ressources about time are available on <URL:http://www.yahoo.com/Science/Weights_and_Measures/Measurements/Time/>. I would exchange GMT for UTC as in the patch below. This patch also removes UCT, assuming that this is the abbreviation for "Universal Coordinated Time", something I have never encountered outside the etcetera file. Markus -- Markus G. Kuhn, Computer Science grad student, Purdue University, Indiana, USA -- email: kuhn@cs.purdue.edu --- etcetera.orig Thu Oct 3 20:08:28 1996 +++ etcetera Thu Oct 3 21:13:49 1996 @@ -1,55 +1,60 @@ # @(#)etcetera 7.5 # All of these are set up just so people can "zic -l" to a timezone # that's right for their area, even if it doesn't have a name or DST rules # (half hour zones are too much to bother with -- when someone asks!) +Zone Etc/UTC 0 - UTC +Link Etc/UTC Etc/Universal +Link Etc/UTC Etc/UTC-0 +Link Etc/UTC Etc/UTC+0 +Link Etc/UTC Etc/UTC0 +Link Etc/UTC Etc/Zulu + +# Since the early 1970s, UTC has been the correct official term for +# the international reference time zone defined in ITU-R +# Recommendation TF.460-4. For old-fashioned British patriots, we +# still offer the classic name of this time zone: + Zone Etc/GMT 0 - GMT -Link Etc/GMT Etc/UTC -Link Etc/GMT Etc/UCT -Link Etc/GMT Etc/Universal Link Etc/GMT Etc/Greenwich -Link Etc/GMT Etc/Zulu -Link Etc/GMT Etc/GMT-0 -Link Etc/GMT Etc/GMT+0 -Link Etc/GMT Etc/GMT0 # We use POSIX-style signedness in the names and output, # internal-style signedness in the specifications. -# For example, TZ=Etc/GMT+4 corresponds to 4 hours _behind_ GMT; -# it is equivalent to TZ=GMT+4, which is implemented directly as per POSIX. +# For example, TZ=Etc/UTC+4 corresponds to 4 hours _behind_ UTC; +# it is equivalent to TZ=UTC+4, which is implemented directly as per POSIX. # Earlier incarnations of this package were not POSIX-compliant, # and had lines such as -# Zone GMT-12 -12 - GMT-1200 +# Zone UTC-12 -12 - UTC-1200 # We did not want things to change quietly if someone accustomed to the old # way does a -# zic -l GMT-12 +# zic -l UTC-12 # so we moved the names into the Etc subdirectory. -Zone Etc/GMT-14 14 - GMT-14 # 14 hours ahead of GMT -Zone Etc/GMT-13 13 - GMT-13 -Zone Etc/GMT-12 12 - GMT-12 -Zone Etc/GMT-11 11 - GMT-11 -Zone Etc/GMT-10 10 - GMT-10 -Zone Etc/GMT-9 9 - GMT-9 -Zone Etc/GMT-8 8 - GMT-8 -Zone Etc/GMT-7 7 - GMT-7 -Zone Etc/GMT-6 6 - GMT-6 -Zone Etc/GMT-5 5 - GMT-5 -Zone Etc/GMT-4 4 - GMT-4 -Zone Etc/GMT-3 3 - GMT-3 -Zone Etc/GMT-2 2 - GMT-2 -Zone Etc/GMT-1 1 - GMT-1 -Zone Etc/GMT+1 -1 - GMT+1 -Zone Etc/GMT+2 -2 - GMT+2 -Zone Etc/GMT+3 -3 - GMT+3 -Zone Etc/GMT+4 -4 - GMT+4 -Zone Etc/GMT+5 -5 - GMT+5 -Zone Etc/GMT+6 -6 - GMT+6 -Zone Etc/GMT+7 -7 - GMT+7 -Zone Etc/GMT+8 -8 - GMT+8 -Zone Etc/GMT+9 -9 - GMT+9 -Zone Etc/GMT+10 -10 - GMT+10 -Zone Etc/GMT+11 -11 - GMT+11 -Zone Etc/GMT+12 -12 - GMT+12 +Zone Etc/UTC-14 14 - UTC-14 # 14 hours ahead of UTC +Zone Etc/UTC-13 13 - UTC-13 +Zone Etc/UTC-12 12 - UTC-12 +Zone Etc/UTC-11 11 - UTC-11 +Zone Etc/UTC-10 10 - UTC-10 +Zone Etc/UTC-9 9 - UTC-9 +Zone Etc/UTC-8 8 - UTC-8 +Zone Etc/UTC-7 7 - UTC-7 +Zone Etc/UTC-6 6 - UTC-6 +Zone Etc/UTC-5 5 - UTC-5 +Zone Etc/UTC-4 4 - UTC-4 +Zone Etc/UTC-3 3 - UTC-3 +Zone Etc/UTC-2 2 - UTC-2 +Zone Etc/UTC-1 1 - UTC-1 +Zone Etc/UTC+1 -1 - UTC+1 +Zone Etc/UTC+2 -2 - UTC+2 +Zone Etc/UTC+3 -3 - UTC+3 +Zone Etc/UTC+4 -4 - UTC+4 +Zone Etc/UTC+5 -5 - UTC+5 +Zone Etc/UTC+6 -6 - UTC+6 +Zone Etc/UTC+7 -7 - UTC+7 +Zone Etc/UTC+8 -8 - UTC+8 +Zone Etc/UTC+9 -9 - UTC+9 +Zone Etc/UTC+10 -10 - UTC+10 +Zone Etc/UTC+11 -11 - UTC+11 +Zone Etc/UTC+12 -12 - UTC+12