Differences between version 21 and predecessor to the previous major change of TimeNotes.
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| Newer page: | version 21 | Last edited on Monday, October 15, 2007 1:27:20 pm | by IanMcDonald | Revert |
| Older page: | version 20 | Last edited on Friday, April 7, 2006 9:29:28 pm | by AlastairPorter | Revert |
@@ -4,13 +4,13 @@
__$__ ls -l /etc/localtime
lrwxrwxrwx 1 root root 33 Apr 22 00:19 __/etc/localtime__ -> __/usr/share/zoneinfo/Pacific/Auckland__
</pre>
-The SuperUser can use tzselect(8) to change these settings. ''Make sure'' it is set correctly! If you have it set to [UTC] your system time will not reflect your localtime. ntpdate(1
) will set the system clock correctly, but the hardware clock will get confused. You can compare these by looking at the output of date(1) and hwclock(8).
+The SuperUser can use [
tzselect(8)]
to change these settings. ''Make sure'' it is set correctly! If you have it set to [UTC] your system time will not reflect your localtime. [
ntpdate(8
)]
will set the system clock correctly, but the hardware clock will get confused. You can compare these by looking at the output of [
date(1)]
and [
hwclock(8)]
.
On [Debian] systems __/etc/default/rcS__ contains a __UTC__ variable that decides whether or not the hardware clock is set to [UTC].
-On [SUSE] systems, __/etc/sysconfig/clock__ defines a __HWCLOCK__ variable that specifies the command-line option hwclock(8) for selecting the clock offset: "-u" for UTC, or "--localtime" for local time.
+On [SUSE] systems, __/etc/sysconfig/clock__ defines a __HWCLOCK__ variable that specifies the command-line option [
hwclock(8)]
for selecting the clock offset: "-u" for UTC, or "--localtime" for local time.
On [RedHat] systems, __/etc/sysconfig/clock__ defines the __UTC__ variable as either __UTC=true__ if the hardware clock is in UTC, or __UTC=false__ if it is in local time.
Having the hardware clock set to UTC is A Good Idea, because it avoids the need to adjust the clock forward or backward an hour when daylight saving goes on or off. There is no standard, ''reliable'' way of recognizing whether the hardware clock has been set for daylight saving or not; hence it is possible, particularly if your machine boots more than one OperatingSystem and you switch between them at the wrong time, for the adjustment to be done twice, or not at all. However, you might be forced to have your hardware clock set to local time in order to maintain compatibility with another OperatingSystem that fiddles with your hardware clock for daylight saving.
@@ -76,17 +76,17 @@
</verbatim>
Find the current time/date for somewhere::
- A really simple way is to set the <tt>TZ</tt> EnvironmentVariable to the timezone you're interested in, then run date(1):
+ A really simple way is to set the <tt>TZ</tt> EnvironmentVariable to the timezone you're interested in, then run [
date(1)]
:
<verbatim>
TZ=Pacific/Auckland date
</verbatim>
Here the value of TZ is a filename path; if it doesn' begin with a __/__, then it is interpreted relative to the __/usr/share/zoneinfo__ directory (on most Linux distros). Multiple files in this directory with the same contents give different ways of specifying the same time zone; thus __NZ__ is a synonym for __Pacific/Auckland__.
-Note that setting __TZ__ in this way can also be used on other commands that show dates/times, such as ls(1), the abovementioned __perl__ and __convdate__ examples etc.
+Note that setting __TZ__ in this way can also be used on other commands that show dates/times, such as [
ls(1)]
, the abovementioned __perl__ and __convdate__ examples etc.
----
Excerpt from comp.risks 22.94:
@@ -98,6 +98,8 @@
[Critical and Significant Dates|http://www.merlyn.demon.co.uk/critdate.htm] contains some interesting dates useful for testing, and also an interesting read.
+----
+See also [NTPNotes]
----
CategoryNotes
