Ready for DST?

  • user warning: Table 'cache' is marked as crashed and should be repaired query: SELECT data, created, headers, expire FROM cache WHERE cid = 'filter:3:fb8d0a948b259ebe1fc47519bbcce0e4' in /home/dowdle/public_html/montanalinux/includes/database.mysql.inc on line 121.
  • user warning: Table 'cache' is marked as crashed and should be repaired query: UPDATE cache SET data = '<p>Daylight Savings Time in the US. Is it the end of the world again March 11th 2007? For most of us our Linux boxes will be just fine. The DST change has been fixed in most modern Linux Distros. But if you are still using your 2.4 kernel based ancient distro, you may want to look into fixing it. That isn\'t what this tip is about rather proof that your box is going to make the switch. You should see this when you run the zdump command below:</p>\n<pre><blockquote>zdump -v /etc/localtime | grep 2007\n/etc/localtime Sun Mar 11 08:59:59 2007 UTC = Sun Mar 11 01:59:59 2007 MST isdst=0 gmtoff=-25200\n/etc/localtime Sun Mar 11 09:00:00 2007 UTC = Sun Mar 11 03:00:00 2007 MDT isdst=1 gmtoff=-21600\n/etc/localtime Sun Nov 4 07:59:59 2007 UTC = Sun Nov 4 01:59:59 2007 MDT isdst=1 gmtoff=-21600\n/etc/localtime Sun Nov 4 08:00:00 2007 UTC = Sun Nov 4 01:00:00 2007 MST isdst=0 gmtoff=-25200</blockquote></pre><p>If you are seeing this then you probably need to fix it some year:</p>\n<pre><blockquote>zdump -v /etc/localtime | grep 2007\n/etc/localtime Sun Apr 1 07:59:59 2007 UTC = Sun Apr 1 01:59:59 2007 CST isdst=0 gmtoff=-21600\n/etc/localtime Sun Apr 1 08:00:00 2007 UTC = Sun Apr 1 03:00:00 2007 CDT isdst=1 gmtoff=-18000\n/etc/localtime Sun Oct 28 06:59:59 2007 UTC = Sun Oct 28 01:59:59 2007 CDT isdst=1 gmtoff=-18000\n/etc/localtime Sun Oct 28 07:00:00 2007 UTC = Sun Oct 28 01:00:00 2007 CST isdst=0 gmtoff=-21600</blockquote></pre><p>At first when I found this tidbit I thought I would be just fine since I run my NTP service to keep good time. Well this technically doesn\'t correct your computers time. The kernel clock uses UTC time not DST. Your computer only translates the DST from UTC time by the TZ database as shown above. So NTP only changes local time not system time.</p>\n', created = 1411141968, expire = 1411228368, headers = '' WHERE cid = 'filter:3:fb8d0a948b259ebe1fc47519bbcce0e4' in /home/dowdle/public_html/montanalinux/includes/database.mysql.inc on line 121.

Daylight Savings Time in the US. Is it the end of the world again March 11th 2007? For most of us our Linux boxes will be just fine. The DST change has been fixed in most modern Linux Distros. But if you are still using your 2.4 kernel based ancient distro, you may want to look into fixing it. That isn't what this tip is about rather proof that your box is going to make the switch. You should see this when you run the zdump command below:

zdump -v /etc/localtime | grep 2007 /etc/localtime Sun Mar 11 08:59:59 2007 UTC = Sun Mar 11 01:59:59 2007 MST isdst=0 gmtoff=-25200 /etc/localtime Sun Mar 11 09:00:00 2007 UTC = Sun Mar 11 03:00:00 2007 MDT isdst=1 gmtoff=-21600 /etc/localtime Sun Nov 4 07:59:59 2007 UTC = Sun Nov 4 01:59:59 2007 MDT isdst=1 gmtoff=-21600 /etc/localtime Sun Nov 4 08:00:00 2007 UTC = Sun Nov 4 01:00:00 2007 MST isdst=0 gmtoff=-25200

If you are seeing this then you probably need to fix it some year:

zdump -v /etc/localtime | grep 2007 /etc/localtime Sun Apr 1 07:59:59 2007 UTC = Sun Apr 1 01:59:59 2007 CST isdst=0 gmtoff=-21600 /etc/localtime Sun Apr 1 08:00:00 2007 UTC = Sun Apr 1 03:00:00 2007 CDT isdst=1 gmtoff=-18000 /etc/localtime Sun Oct 28 06:59:59 2007 UTC = Sun Oct 28 01:59:59 2007 CDT isdst=1 gmtoff=-18000 /etc/localtime Sun Oct 28 07:00:00 2007 UTC = Sun Oct 28 01:00:00 2007 CST isdst=0 gmtoff=-21600

At first when I found this tidbit I thought I would be just fine since I run my NTP service to keep good time. Well this technically doesn't correct your computers time. The kernel clock uses UTC time not DST. Your computer only translates the DST from UTC time by the TZ database as shown above. So NTP only changes local time not system time.