new Daylight Saving Time dates

dux0r · 12-04-2006, 03:11 PM

Daylight Saving Time will occur on dates in 2007 that don't conform to the old standards.

from Wikipedia:

Quote:

DST commonly begins in the northern hemisphere on the last Sunday in March or the first Sunday in April, and ends on the last Sunday in October. However, due to the Energy Policy Act of 2005, beginning in 2007, the United States will begin observing DST from the second Sunday in March until the first Sunday in November. (Studies will determine if this remains permanent.)

What files tell Linux which dates to spring forward and fall back? Will I replace files or change configurations? I tested a server in the office and it's currently configured to spring forward on 4/1/2007 rather than 3/11/2007.

This is my first Linux question, please be gentle.

derxob · 12-04-2006, 04:22 PM

Welcome to the forums!

I'd suggest a 'swifter' alternative to worrying about dates/times all the time.

Check out "ntpdate" - It is a network time protocol that you can set to poll a specific "time server" and it will automagically adjust your time. For example, on my servers, I have a bootup script run "ntpdate time.nist.gov" every time the machine is rebooted, which keeps it in sync with the time according to the National Institute of Standards and Technology.

IBall · 12-04-2006, 06:35 PM

I think even using ntp, you need to tell it about daylight savings.

If you are using Debian, get the new tzdata package from Unstable. This may include updates for your time zone if your change dates have changed. Just install it, and everything should work properly. This package also works on Ubuntu.

I hope this helps
--Ian

osor · 12-04-2006, 10:53 PM

Quote:

Originally Posted by dux0r

What files tell Linux which dates to spring forward and fall back? Will I replace files or change configurations?

It depends on what distribution you use (or more importantly, what C library your system uses). For most glibc implementations, timezone info is stored in a zoneinfo database (/usr/share/zoneinfo or similar). AFAIK, the same goes for BSD libc implementations. Some embedded c libraries may be different (e.g., uClibc 0.9.28 lacks tzfile() capabilities, and requires the setting of the TZ environment variable or existence of /etc/TZ file. for example, this applies to the OpenWRT Project). Generally, your distro vendor should provide up-to-date zoneinfo databases. If not, you can probably get appropriate files and/or utilities from either glibc or a public provider such as ftp://elsie.nci.nih.gov/pub.

Quote:

Originally Posted by dux0r

I tested a server in the office and it's currently configured to spring forward on 4/1/2007 rather than 3/11/2007.

Are you sure? How did you test it? If you have a modern distro, you should be able to see past and future dates using zdump. For example, on my machine,

Code:

root@localhost # zdump -v EST5EDT | grep 2007
EST5EDT  Sun Mar 11 06:59:59 2007 UTC = Sun Mar 11 01:59:59 2007 EST isdst=0
EST5EDT  Sun Mar 11 07:00:00 2007 UTC = Sun Mar 11 03:00:00 2007 EDT isdst=1
EST5EDT  Sun Nov  4 05:59:59 2007 UTC = Sun Nov  4 01:59:59 2007 EDT isdst=1
EST5EDT  Sun Nov  4 06:00:00 2007 UTC = Sun Nov  4 01:00:00 2007 EST isdst=0

slackamp · 12-08-2006, 10:15 AM

is this tied to compilation of glibc? so if i just update the /usr/share/zoneinfo from another box would this work?

steinz · 12-28-2006, 02:11 PM

for this kind of update, do I need to bring down my database first?