Ready for DST?

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.