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Daylight Savings Time settings in Linux

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Notes on how to view or change the Daylight Savings Time settings on Linux.

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Last updated: 8 June 2007

The conditions for the beginning and end of Daylight Savings Time (DST) in the United States have changed, starting in 2007. You can view the DST settings on your machine by opening up a command shell and giving the following command:

 zdump -v /etc/localtime | grep 2007

This should produce something like:

/etc/localtime  Sun Mar 11 06:59:59 2007 UTC = Sun Mar 11 01:59:59 2007 EST isdst=0 gmtoff=-18000
/etc/localtime  Sun Mar 11 07:00:00 2007 UTC = Sun Mar 11 03:00:00 2007 EDT isdst=1 gmtoff=-14400
/etc/localtime  Sun Nov  4 05:59:59 2007 UTC = Sun Nov  4 01:59:59 2007 EDT isdst=1 gmtoff=-14400
/etc/localtime  Sun Nov  4 06:00:00 2007 UTC = Sun Nov  4 01:00:00 2007 EST isdst=0 gmtoff=-18000

If you don't see DST starting on March 11 2007 then you need to update your settings. How you do this will depend on your Linux distribution.

(Note that possibility of using a full-path filename on the zdump command line in place of a timezone name is not documented in the zdump man page.)

Fedora/Red Hat

Using RPM I found that the file /etc/localtime is a file owned by the package glibc, rather than a soft link to a file for my particular timezone. Updating that package got me the proper settings. Simply updating the tzdata was not sufficient.

Other Distributions

I don't know the details for other distributions, but I'll post anything useful someone cares to send me if it's significantly different from Fedora/Red Hat.  

Copyright © 2007 by Spy Hill Research

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Last modified: 08 June 2007