06-03-2008
How can I find my current Daylight Saving offset?
Hello all,
I'm having a problem where a script needs to calculate GMT time given local time. For 6 months, that's easy. The other 6 months, it's not, as I have to add an extra hour to allow for Daylight Saving. At the moment, I manually add and remove an offset but, for obvious reasons, I'd prefer to automate this.
I was surprised that I couldn't find much discussion on this. What I'm looking for is some way to determine what the current local offset from GMT is. There is talk of an environment variable, $TZ, that includes information on the application of the summer time shift, but I cannot see this variable anywhere on my RHEL or Ubuntu machines.
So, is there a nice easy way to work out my current offset and therefore modify the size of the GMT shift I need. I'm thinking of using a cron, triggered at 0400 six months a year, to create $TZ or similar, but that would be ugly and just plain wrong for up to a day if I need to reboot during the summer!
Thanks!
10 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
Hello!
I'm currently working on a climatological dataset that uses unix-timestamp and a real date like 28/03/2004 02:45:00 h. in spring the unix-timestamp follows its continuos mode but in the column of the real date the time jumps one hour forward (e.g. from 1:59:59 to 3:00:00). i think this is... (1 Reply)
Discussion started by: softmachine
1 Replies
2. Solaris
hi ...
i have an E450 sun server that is running solaris 6 . i want to disable daylight savings on my server .
My question is :
1) how to know that my server is running daylight savings ?
2) how to disable it ?
my zoneinfo file contains the following
# @(#)init.dfl 1.2 92/11/26
#
#... (1 Reply)
Discussion started by: ppass
1 Replies
3. AIX
On AIX 5.1, after applying a DST patch or workaround, is there a way to test that the DST changes have taken effect? (1 Reply)
Discussion started by: dangral
1 Replies
4. AIX
Hi all
We are currently using AIX 5.3, we reuquire to change the time according to the daylight saving scenario. We are using the internal clock and are not synced with ntp server. Can any one please tell me how to do that without effecting the processes running on the servers? (1 Reply)
Discussion started by: masquerer
1 Replies
5. HP-UX
I have a problem with the time so I need to set the DST to be OFF. is anybody can show me how to set the DST to be OFF? (11 Replies)
Discussion started by: Billy_yuli
11 Replies
6. UNIX for Dummies Questions & Answers
The daylight saving action is not working
Time zone was set for that Australia(parth) and issued reboot.
Now for DST, (Daylight Saving Time):
For 29 Oct 2006 (sunday) day, if set time is 1:59:00 than after 1 minute it will
become 3:00:00 as per DST . This was found to be happening.i.e DST... (1 Reply)
Discussion started by: subratasaharia
1 Replies
7. UNIX for Advanced & Expert Users
The daylight saving action is not working
Time zone was set for that Australia(parth) and issued reboot.
Now for DST, (Daylight Saving Time):
For 29 Oct 2006 (sunday) day, if set time is 1:59:00 than after 1 minute it will
become 3:00:00 as per DST . This was found to be happening.i.e DST... (1 Reply)
Discussion started by: subratasaharia
1 Replies
8. Linux
Hi folks,
I would like to read the start date and end date of the Daylight Saving Time for the given timezone in the given year. What's the function in C/C++ to read the start of the Daylight Saving date and end of Daylight saving date?
I'm using Linux 2.6.xx Kernel.
For Example, in... (4 Replies)
Discussion started by: suryaemlinux
4 Replies
9. Linux
Hi,
I have few doubt on daylight saving.
Can any one clarify the below points.
1) How to configure daylight saving(DLS) time ?
2) How to query DLS ?
3) If i set DLS(say some how) will it be autometically changed or user has to manually change system time ?
I got few info on net about... (3 Replies)
Discussion started by: ashokd001
3 Replies
10. Solaris
Hello,
Quick question: How do I verify if my Solaris 11 hosts/zones, configured with NTP, would change automatically to the DST?
Thanks! (1 Reply)
Discussion started by: feroccimx
1 Replies
CRON(8) BSD System Manager's Manual CRON(8)
NAME
cron -- daemon to execute scheduled commands (Vixie Cron)
SYNOPSIS
cron [-s] [-o] [-x debugflag[,...]]
DESCRIPTION
The cron utility is launched by launchd(8) when it sees the existence of /etc/crontab or files in /usr/lib/cron/tabs. There should be no
need to start it manually. See /System/Library/LaunchDaemons/com.vix.cron.plist for details.
The cron utility searches /usr/lib/cron/tabs for crontab files which are named after accounts in /etc/passwd; crontabs found are loaded into
memory. The cron utility also searches for /etc/crontab which is in a different format (see crontab(5)).
The cron utility then wakes up every minute, examining all stored crontabs, checking each command to see if it should be run in the current
minute. When executing commands, any output is mailed to the owner of the crontab (or to the user named in the MAILTO environment variable
in the crontab, if such exists).
Additionally, cron checks each minute to see if its spool directory's modification time (or the modification time on /etc/crontab) has
changed, and if it has, cron will then examine the modification time on all crontabs and reload those which have changed. Thus cron need not
be restarted whenever a crontab file is modified. Note that the crontab(1) command updates the modification time of the spool directory
whenever it changes a crontab.
Available options:
-s Enable special handling of situations when the GMT offset of the local timezone changes, such as the switches between the standard
time and daylight saving time.
The jobs run during the GMT offset changes time as intuitively expected. If a job falls into a time interval that disappears (for
example, during the switch from standard time) to daylight saving time or is duplicated (for example, during the reverse switch),
then it is handled in one of two ways:
The first case is for the jobs that run every at hour of a time interval overlapping with the disappearing or duplicated interval.
In other words, if the job had run within one hour before the GMT offset change (and cron was not restarted nor the crontab(5)
changed after that) or would run after the change at the next hour. They work as always, skip the skipped time or run in the added
time as usual.
The second case is for the jobs that run less frequently. They are executed exactly once, they are not skipped nor executed twice
(unless cron is restarted or the user's crontab(5) is changed during such a time interval). If an interval disappears due to the GMT
offset change, such jobs are executed at the same absolute point of time as they would be in the old time zone. For example, if
exactly one hour disappears, this point would be during the next hour at the first minute that is specified for them in crontab(5).
-o Disable the special handling of situations when the GMT offset of the local timezone changes, to be compatible with the old (default)
behavior. If both options -o and -s are specified, the option specified last wins.
-x debugflag[,...]
Enable writing of debugging information to standard output. One or more of the following comma separated debugflag identifiers must
be specified:
bit currently not used
ext make the other debug flags more verbose
load be verbose when loading crontab files
misc be verbose about miscellaneous one-off events
pars be verbose about parsing individual crontab lines
proc be verbose about the state of the process, including all of its offspring
sch be verbose when iterating through the scheduling algorithms
test trace through the execution, but do not perform any actions
FILES
/usr/lib/cron/tabs Directory for personal crontab files
SEE ALSO
crontab(1), launchctl(1), crontab(5), launchd.plist(5), launchd(8)
AUTHORS
Paul Vixie <paul@vix.com>
BSD
June 17, 2007 BSD