Differences between current version and revision by previous author of UTC.
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| Newer page: | version 17 | Last edited on Wednesday, November 10, 2004 6:07:20 am | by AristotlePagaltzis | |
| Older page: | version 14 | Last edited on Tuesday, October 14, 2003 2:10:18 pm | by JohnMcPherson | Revert |
@@ -1,28 +1,8 @@
-An [Acronym] for __U__niversale __T__emps __C__oordinee
, ie Coordinated Universal Time.
+An [Acronym] for __U__niversale __T__emps __C__oordineé
, ie Coordinated Universal Time.
-This is the standard time zone all other time zones are based on. It replaced [GMT] in the early 1970s. [UTC] is measured with atomic clocks. It is kept within .9 seconds of [TAI], but with an integral number of leap seconds added occasionally to reflect the season at and location on the planet. This way [UTC] stays in sync with the rotation of the earth, making sure midnight always occurs at the same time relative to the stars.
+This is the standard time zone all other time zones are based on. It replaced [GMT] in the early 1970s. [UTC] is measured with atomic clocks. It is kept within .9 seconds of [TAI], but with an integral number of leap seconds added occasionally to reflect the season at and location on the planet. This way [UTC] stays in sync with the rotation of the earth, making sure midnight always occurs at the same time relative to the stars. To date all corrections have been positive to account for the tidal drag on the earth which slows the planet down
.
-To date all corrections have been positive to account for the tidal drag on the earth which slows the planet down.
-
-For more information see http
://tycho.usno.navy.mil/systime.html
-
-Compare
[GMT], [TAI].
-----
-;Extract from comp.risks 22.94...: Motorola reports that several GPS receivers in its Oncore line will misdisplay the date on 28 Nov 2003 at midnight UTC. For a one-second window the receivers will mistakenly report the date as 29 Nov instead of 28 Nov.
-
-;:Here's why. Every couple of years or so
for the past three decades, the International Earth Rotation Service has announced a leap-second because the Earth is rotating slightly more slowly than an 86400-second day would suggest. But since 1 Jan 1999, we've had an unusually long dry spell without any leap seconds. The GPS week number in the UTC correction parameter is 8 bits long, which allows for 256 weeks of unambiguous time calculation. Until now this parameter has never rolled over, but because of the dry spell 28 Nov will be exactly 256 weeks after the most recent leap second, and the rollover will contribute to the bug. <http://www.motorola.com/ies/GPS/docs_pdf/notification_oncore.pdf>
-
-;:Steve Allen writes in <http://www.ucolick.org/~sla/leapsecs/onlinebib.html> that some JDAM smart bombs and other munitions are rumored to contain these receivers. Anyone intending to use those weapons around the magic window might want to reschedule their bombing runs for some other time. ...
-
-----
-
-[Unix
] systems
and cousins traditionally store times as [UTC], and convert them according to the local timezone settings only
for display. On a typical [Linux] machine, __/etc/timezone__ contains the time zone (such as __Pacific/Auckland__), and __/etc/localtime__ is a SymLink to a binary file containing information on the standard and the daylight savings offset of that time zone, as well instructions on how to calculate when daylight savings is in effect. In the above-mentioned example it might look like this:
-
- __/etc $__ ls -l localtime
- lrwxrwxrwx 1 root root 33 Apr 22 00:19 __localtime__ -> __/usr/share/zoneinfo/Pacific/Auckland__
-
-The SuperUser can use tzselect(1) to change these settings.
-
-Also, __/etc/default/rcS__ (on [Debian] systems at least) contains a __UTC__ variable to tell your OperatingSystem whether or not your hardware clock is set to [UTC]. Doing so and setting __UTC=yes__ is A Good Idea.
-
-For
more about setting up your machine's clock, see TimeNotes,
[NTP
] and HowToClock
.
+See also
:
+*
[GMT], [TAI] for comparison
+*
[NTP
] and TimeNotes
for more about setting up your machine's clock
+*
[Systems of Time | http://tycho.usno.navy.mil/systime.html
].
