09-20-2004
Winter/Summer time change
Reliant Unix.
Our branch in Syria has a Unix Server running our company application.
Usually the the time is changed not in a fixed date.....but around end of October and beginning of November.
The night of the summer winter time change last year...we put the server in singel user mode, then we change the /etc/TIMEZONE file to:
TZ=GMT-2Syria and we booted, and after that the time was added one hour...GREAT. One week later we were surprised that the time was added again one hour automatically (according to the Asian summber winter time it seems....!!!) so we had to shutdown the server again and put the TZ as GMT-3Syria.
For this year and after some investigation we decided to do the following:
Next month we will have time change from summer time which is [GMT + 3] in local
time to winter time [GMT + 2], this time change will be done by changing the TZ
parameter in the /etc/TIMEZONE and reboot the system the suggested TZ is:
TZ=Syr-2SyrDST,M4.1.5/04:00:00,M10.1.5/05:00:00
With this TZ the time will be changed from GMT+2 to GMT+3 on the first Friday from April at 04:00:00AM (from 04:00:00 to 05:00:00) and from the GMT+3 to GMT+2 on the first Friday from October at 05:00:00AM (from 05:00:00 to 04:00:00), my question is:
- Is the above mentioned TZ parameter with the description correct?
- With the above mentioned TZ is there any configuration file involved in the time change and the daylight saving control?
- Can we guarantee that the time won't be changed automatically with the local time zone if we implement the above mentioned TZ?
Sorry if this was very boring....
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rtc(1M) System Administration Commands rtc(1M)
NAME
rtc - provide all real-time clock and GMT-lag management
SYNOPSIS
/usr/sbin/rtc [-c] [-z zone-name]
DESCRIPTION
On x86 systems, the rtc command reconciles the difference in the way that time is established between UNIX and MS-DOS systems. UNIX systems
utilize Greenwich Mean Time (GMT), while MS-DOS systems utilize local time.
Without arguments, rtc displays the currently configured time zone string. The currently configured time zone string is based on what was
last recorded by rtc-z zone-name.
The rtc command is not normally run from a shell prompt; it is generally invoked by the system. Commands such as date(1) and rdate(1M),
which are used to set the time on a system, invoke /usr/sbin/rtc -c to ensure that daylight savings time (DST) is corrected for properly.
OPTIONS
-c This option checks for DST and makes corrections if necessary. It is normally run once a day by a cron job.
If there is no RTC time zone or /etc/rtc_config file, this option will do nothing.
-z zone-name This option, which is normally run by the system at software installation time, is used to specify the time zone in which
the RTC is to be maintained. It updates the configuration file /etc/rtc_config with the name of the specified zone and the
current GMT lag for that zone. If there is an existing rtc_config file, this command will update it. If not, this command
will create it.
FILES
/etc/rtc_config The data file used to record the time zone and GMT lag. This file is completely managed by /usr/sbin/rtc, and it is
read by the kernel.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Architecture |x86 |
+-----------------------------+-----------------------------+
|Availability |SUNWcsu |
+-----------------------------+-----------------------------+
SEE ALSO
date(1), rdate(1M), attributes(5)
SunOS 5.10 3 Oct 2003 rtc(1M)