+[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, <tt> /etc/timezone</tt> contains the time zone (such as <tt> Pacific/Auckland</tt> ), and <tt> /etc/localtime</tt> 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: 

+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 <tt> /etc/default/rcS</tt> contains a <tt> UTC</tt> variable that decides whether or not the hardware clock is set to [UTC]. 

+On [SUSE] systems, <tt> /etc/sysconfig/clock</tt> defines a <tt> HWCLOCK</tt> variable that specifies the command-line option [ hwclock(8)] for selecting the clock offset: <tt> -u</tt> for [ UTC] , or <tt> --localtime</tt> for local time. 

+On [RedHat] systems, <tt> /etc/sysconfig/clock</tt> defines the <tt> UTC</tt> variable as either <tt> UTC=true</tt> if the hardware clock is in UTC, or <tt> UTC=false</tt> if it is in local time. 

+Having the hardware clock set to [ UTC] is [ A Good Idea|BadIdea] , 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. 

+ perl -e 'print localtime( ''<unix timestamp>'' ) . "\n"'  

+ perl -e 'print gmtime( ''<unix timestamp>'' ) . "\n"' # for UTC 

+ (<tt> convdate</tt> is part of the <tt> inn</tt> package.) 

+ A really simple way is to set the <tt>TZ</tt> EnvironmentVariable to the timezone you're interested in, then run [ date(1)] : 

+Here the value of TZ is a filename path; if it doesn' begin with a <tt> /</tt> , then it is interpreted relative to the <tt> /usr/share/zoneinfo</tt> directory (on most Linux distros). Multiple files in this directory with the same contents give different ways of specifying the same time zone; thus <tt> NZ</tt> is a synonym for <tt> Pacific/Auckland</tt> . 

+Note that setting <tt> TZ</tt> in this way can also be used on other commands that show dates/times, such as [ ls(1)] , the abovementioned <tt> perl</tt> and <tt> convdate</tt> examples etc.