topic Re: Time Change Question in Operating System - Linux

Time Change Question

P_F — Fri, 31 Oct 2008 17:50:01 GMT

I'm unsure whether my servers will automatically adjust for Daylight Saving Time change in the fall of 2008.

When I issue the date command this is what appears:

[root@XXXXXXX ~]# date
Fri Oct 31 14:44:30 EDT 2008

Re: Time Change Question

Matti_Kurkela — Fri, 31 Oct 2008 19:02:36 GMT

To confirm that, you would need to find out your current timezone setting. You posted to a Linux forum, so I'll assume your question is about Linux systems.

Too bad you did not disclose the name of your Linux distribution (i.e. RedHat, SuSE, Debian etc.).

In a Linux system, the timezone setting is usually in the form "Continent/Capital", e.g. "America/New_York".

If you're using RedHat (or Centos, or some other RedHat-like Linux), look into /etc/sysconfig/clock. It is a text file that contains system clock settings, including the timezone.

After you know your timezone setting, run "zdump -v Continent/Capital". It will list the exact times of Daylight Saving Time change as they're defined in your system for that particular timezone. Both past and future DST change times will be listed.

For example:
zdump -v America/New_York
displays this on my system:
...
America/New_York Sun Nov 2 05:59:59 2008 UTC = Sun Nov 2 01:59:59 2008 EDT isdst=1 gmtoff=-14400
America/New_York Sun Nov 2 06:00:00 2008 UTC = Sun Nov 2 01:00:00 2008 EST isdst=0 gmtoff=-18000
...

If my system was using the America/New_York timezone, it would change from DST to standard time on next Sunday, so that after 01:59:59 EDT comes 01:00:00 EST.

MK

Re: Time Change Question

P_F — Fri, 31 Oct 2008 20:43:37 GMT

Apologies for excluding the required info.
The box is Red hat.

According to

[root@X ~]# cat /etc/sysconfig/clock
ZONE="America/New_York"
UTC=false
ARC=false

and

# zdump -v America/New_York

America/New_York Sun Mar 8 07:00:00 2037 UTC = Sun Mar 8 03:00:00 2037 EDT isdst=1 gmtoff=-14400
America/New_York Sun Nov 1 05:59:59 2037 UTC = Sun Nov 1 01:59:59 2037 EDT isdst=1 gmtoff=-14400
America/New_York Sun Nov 1 06:00:00 2037 UTC = Sun Nov 1 01:00:00 2037 EST isdst=0 gmtoff=-18000
America/New_York 9223372036854689407 = NULL
America/New_York 9223372036854775807 = NULL

#########################

So, am I reading this correctly ? to say it will switch to EST on

Sun Nov 1 01:00:00

Re: Time Change Question

Matti_Kurkela — Fri, 31 Oct 2008 21:23:39 GMT

Note the year: according to the lines you showed, if the system is still using the current rules on year 2037, it will switch to EST on Sun Nov 1 of 2037. The switch will happen so that 01:59:59 EDT will be followed by 01:00:00 EST.

In other words, the transition will happen on 02:00:00 EDT = 01:00:00 EST.

Use "zdump -v America/New_York | grep 2008" to get the entries for this year only.

Based on the indicated transition date for 2037, your system already has the correct DST rules: the DST will end on the first Sunday of November. This year, it will be Sun Nov 2.

MK

Re: Time Change Question

P_F — Fri, 31 Oct 2008 21:51:43 GMT

Ah, ya. Just noticed the year 2037.

Anyway, thanks a lot.

Re: Time Change Question

P_F — Mon, 03 Nov 2008 13:54:10 GMT

Refer to thread above.