Slashdot Log In
Linux Systems and the New DST
Posted by
kdawson
on Tue Mar 06, 2007 08:58 AM
from the spring-forward-fall-flat dept.
from the spring-forward-fall-flat dept.
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."
Related Stories
[+]
Technology: 'Daylight Savings Bugs' Loom 403 comments
An anonymous reader writes "ZDNet has front page coverage of the looming daylight savings changeover, and the bugs that may crop up this year. With the extension of daylight savings time by four weeks, some engineers and programmers are warning that unprepared companies will experience serious problems in March. While companies like Microsoft have already patched their software, Gartner is warning that bugs in the travel and banking sectors could have unforeseen consequences in the coming months. ' In addition, trading applications might execute purchases and sales at the wrong time, and cell phone-billing software could charge peak rates at off-peak hours. On top of that, the effect is expected to be felt around the world: Canada and Bermuda are conforming to the U.S.-mandated change, and time zone shifts have happened in other locales as well.'" Is this just more Y2K doomsaying, or do you think there's a serious problem here?
[+]
Microsoft Charging Businesses $4K for DST Fix 395 comments
eldavojohn writes "Microsoft has slashed the price it's going to charge users on the daylight saving time fixes. As you know, the federal law that moves the date for DST goes into effect this month. Although the price of $4000 is 1/10 of the original estimate Microsoft made, it seems a bit pricey for a patch to a product you've already paid for. From the article: 'Among the titles in that extended support category are Windows 2000, Exchange Server 2000 and Outlook 2000, the e-mail and calendar client included with Office 2000. For users running that software, Microsoft charges $4,000 per product for DST fixes. For that amount, customers can apply the patches to all systems in their organizations, including branch offices and affiliate.' The only thing they can't do, said a Microsoft rep, is redistribute them."
This discussion has been archived.
No new comments can be posted.
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
Full
Abbreviated
Hidden
Loading... please wait.
Simple (Score:5, Interesting)
Beware JVM Problems (Score:5, Informative)
Parent
Re: (Score:3, Informative)
You can set a Windows box to GMT...
Re:Simple (Score:4, Interesting)
Tell that to my Outlook calendar. In two weeks when I host my telecon involving people from several states around the US, how many do you think are going to call on time, an hour early, or an hour late? I'm not looking forward to repeating myself over and over. Besides, 4k is chump change when you're talking about the time wasted when dozens of meetings get screwed up (mainly due to PEBKAC errors, but still.)
Parent
Windows-only "Y2DST" bugs (Score:4, Informative)
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?".
Parent
A very simple *nix test (Score:5, Informative)
$ 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.
Solaris Test (was Re:A very simple *nix test) (Score:3, Informative)
For Solaris you can still use zdump, just with a timezone entry instead of /etc/localtime:
zdump -v US/Eastern | grep 2007
From BigAdmin [sun.com]
Re:Looks like I'm screwed then (Score:5, Funny)
Parent
Win vs Lin (Score:5, Informative)
Re:Win vs Lin (Score:5, Funny)
Parent
Re:Win vs Lin (Score:5, Insightful)
Exactly. All the competent Windows admins have already switched to Linux.
Parent
Re:Win vs Lin (Score:4, Insightful)
Parent
Multiple timezone meetings (Score:4, Informative)
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.
Parent
NTP? (Score:4, Interesting)
Re:NTP? (Score:5, Informative)
However, if you're using an old zoneinfo file for local time, the interpretation of that UTC time is something else again, and NTP won't help you at all.
(Well, assuming you don't live in Arizona or Hawaii. Indiana's timing sucks, doesn't it?)
Parent
Re:NTP? (Score:5, Informative)
NTP as a protocol tracks the number of seconds elapsed since 1 January, 1900 UTC. It has absolutely zero knowledge of timezones or what they mean. Your NTP daemon of choise just sits there keeping your system clock reasonably accurate with UTC time and it's the relevant libc C time functions that read that UTC time, then read in the set zoneinfo data, and combine the two to give you and your apps local time.
Parent
Root Cause (Score:5, Insightful)
How many of you, after all, have told your State legislatures that this is stupid and it's time to opt out?
Re:Root Cause (Score:5, Insightful)
I like DST. I know how to set what clocks I have that still need to be changed. I enjoy the extra light at the end of the day. I am aware that I could just get up an hour early and try to convince everyone else that I have to deal with to do the same, but DST accomplishes that. Also, I live in a city that spans state lines, so having one state opt out would be a real hassle.
I would much rather lobby my legislature to allow wine to be shipped directly to my door. For crying out loud, I can get ammo delivered (and left on the doorstep) without even a signature, why can't I buy wine directly.
So, for all of those who dislike DST, try this: Just get up an hour later.
Parent
Better article (Score:3, Informative)
How may we help you? (Score:5, Funny)
"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......."
How to verify whether your system is up to date (Score:4, Informative)
The short answer... (Score:4, Informative)
cd
wget --passive-ftp ftp://elsie.nci.nih.gov/pub/tzdata2007c.tar.gz [nih.gov]
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 worried... (Score:4, Insightful)
I'm coming four hours early.
Recent? It was two years ago... (Score:5, Insightful)
Re:A problem with DST in general (Score:4, Informative)
For most of human history, time meant local solar time, or time by the moon and stars. It isn't until the mid 18th C. that the "longitude problem" is solved by the invention of precision marine chronometers. It isn't until the mid 19th C. that the "standard time" demanded by the telegraph, the railroad, trade and industry, intrudes on the lives of ordinary people.
Parent