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Linux Systems and the New DST
An anonymous reader writes "The recent changes in the Daylight Saving Time will affect virtually all computer systems in the US one week from now. Microsoft has been busy preparing Windows users for 'Y2DST,' and all the major Linux distributions have also issued patches. How can you be sure your Linux systems are ready, and what can you do to get them ready if they're not? This how-to article at Linux-Watch answers both questions in simple language and with easy-to-follow instructions."
Set you system to run on UTC. No daylight savings hassles to worry about.
Oh, no! You have walked into the slavering fangs of a lurking grue!
$ date --date="Mar 25 15:00:00 UTC 2006"
$ date --date="Mar 25 15:00:00 UTC 2007"
If the output of both shows the same time (eg. 10:00 EST) then you've got a problem. If they show different times (eg. 10:00 EST and 11:00 EDT) then your system is ok.
Funny how with Linux there isn't any danger of your entire system breaking. I know we spent every day since the Windows patches were relased, testing and make sure the patches don't break anything. So far our Exchange server had to be restored from backup once already b/c all the calendar entries got screwed up.
How does this work with NTP? Will the system just stay up-to-date from another system that understands the new rules, or does NTP all work on UTC so that it's not aware of this, or something?
How many of you, after all, have told your State legislatures that this is stupid and it's time to opt out?
Lacking <sarcasm> tags,
If you have systems running JVM 1.3 that interact with systems using 1.4 or above, beware, there are issues in how they implemented the fix in 1.3. In Java 1.3, the DST change is applied to ALL years, including prior to 2007, so if you have a remote object on 1.3 give a date to an application running in 1.4 (as a binary object, not just text) then it will cause problems, it will set it to 1 hour off, if you don't use timestamps, the default will be midnight, so one hour off will be the previous day. This has caused a bunch of problems where I work.
For Solaris you can still use zdump, just with a timezone entry instead of /etc/localtime:
zdump -v US/Eastern | grep 2007
From BigAdmin
The jModule
"Hello - this is Manny and I will be your corporate level support concierge for this session - how may I help you?"
"Oh, Hi Manny, this is Stuart and I'm at our corporate IT HQ. We need help with the new DST configuration, please."
"Ok, Stuart, I'll be happy to provide whatever help I can, if you will just tell me the name of the corporation you're with, along with the contract ID and your callback number, you can hang up and I'll call you back so we can get things started."
"Ummm...Manny...excuse me, but I've never quite understood why you people always ask for the name of the corporation right off...what's up with that, if I may ask?"
"Well, Stuart, in our effort to provide the best quality service, we need to know upfront which company we are serving so we can insure that our responses fit with such things as non-disclosures, corporate culture, etc. As an example, since this incident deals with DST, if you are with Siemens, we're instructed to use twenty-four hour time, such as the time now being sixteen-forty-two hundred hours. If you are with Hertz Car Rental, the time is four forty-two pm."
"Oh, I see. Well, I'm with Microsoft, Manny, so what does the system say you should tell me?"
"Microsoft - I see. Well, Stuart, the big hand is on the four and the little hand is......."
Actually this isn't a problem with any OS or the computer industry. It is a problem with Daylight Savings Time. Man has been telling time for centuries and it wasn't until the DST mess that we started having issues. This is on the same lines as the US not using the metric system.
Skipping all the crap and presuming you have an older distro that doesn't to automatic updates, I'll summarize the steps needed (Do this at your own risk, but it should work on any even remotely standard distro, even very old ones):
/tmp /usr/share/zoneinfo/EST5EDT /etc/localtime
;-)
/etc/localtime | grep 2007
cd
wget --passive-ftp ftp://elsie.nci.nih.gov/pub/tzdata2007c.tar.gz
tar -xzvf tzdata2007c.tar.gz
zic northamerica
ln -sf
If you live outside the civilized world, insert the appropriate time zone in place of EST5EDT.
And finally, verify it with:
zdump -v
Which should say "Mar 11" and "Nov 4"
I'm coming four hours early.
It's not wasting time, I'm educating myself.
It was two years ago that this was signed into affect... this shouldn't be the rush that Microsoft, Cisco, and all the rest are making it. Slackers wasted one and a half years doing almost nothing... and now we get this.
You're posting to Slashdot about a problem with a date? And you think you're gonna get screwed? I'm not sure if this is redundant or wishful thinking. :)
If events are scheduled using UTC, then timezone and dst make no difference.
But if Outlook has "Y2DST" bugs, it stores or assumes that date/time is in local time, so events may be wrong if DST or the timezone of your server changes.
Note that these bugs if they exist could be reproduced otherwise by changing the timezone while programs are running. Events should happen at the same time, independent of timezone. (A real situation would be flying a live system/laptop to a new timezone).
But the bug in Windows is at a low level. Windows, for backward compatibility to DOS, assumes the hardware clock is local time. Any program that depends directly on the local time here, needs more than trivial algorithms to handle timezone and DST algorithms. These algorithms will fail, obviously if DST unexpectedly changes, and are probably in general not really expecting timezone to change. ( These algorithms could be compared with Y99-Y2K algorithms that tried to convert from a two digit year).
And obviously any programs that have such low level DST/Timezone handling code would fail if someone set the not often used RealTimeIsUniversal=1 in Windows.
In general no program should rely on local time, internally. Local time should only be used to convey information to the user. "You appointment is at XXX in your timezone", or "What time in your timezone would you like to schedule your meeting alarm?".
It's not possible to get a perfect solution to the problem. The best design I've seen stores times in UTC, together with a description of the entry timezone and the offset. Each user has a current local timezone (and it's assumed that users who travel will track these problems for themselves). When a change to DST comes along, the administrator can do some or all of the following:
The system also allows users to override the entry timezone on a per-entry basis. This means that I can enter a meeting in the UK marked as 9am Atlanta time, and be confident that it'll not only appear properly, but that if Atlanta's timezone changes on me, it'll be updated properly.
I appear to have a blog. Odd.