How to check if the Time Zone database (often called tz or zoneinfo or tzdata ) has the right daylight savings or summer time (DST) change over dates?

Solution Verified - Updated -


  • Red Hat Enterprise Linux (RHEL) 4
  • Red Hat Enterprise Linux (RHEL) 5
  • Red Hat Enterprise Linux (RHEL) 6


  • How to check if the timezone data has the right daylight savings or summer time changeover dates?
  • How to check the offset and drift values for tzdata package?


  • The timezone information, including changeover dates for daylight savings and summer time (DST), is included in the tzdata package.

  • The Time Zone Database contains code and data that represent the history of local time for many representative locations around the globe.

  • It is updated periodically to reflect changes made by political bodies to time zone boundaries, UTC offsets, and daylight-saving rules.

  • Check the version of the tzdata package which is installed on the machine, with the following command:

# rpm -q tzdata
  • This reports the year and revision of the files in use and it means that the installed timezone files date from 2009, and are at revision u.

  • To view the changeover dates for DST in a particular timezone:

# zdump -v /usr/share/zoneinfo/<Region>/<Timezone> | grep <year> 
  • This will give a list of the changeover dates such as the following:
# zdump -v /usr/share/zoneinfo/America/Los_Angeles | grep 2010
/usr/share/zoneinfo/America/Los_Angeles  Sun Mar 14 09:59:59 2010 UTC = Sun Mar 14 01:59:59 2010 PST isdst=0 gmtoff=-28800
/usr/share/zoneinfo/America/Los_Angeles  Sun Mar 14 10:00:00 2010 UTC = Sun Mar 14 03:00:00 2010 PDT isdst=1 gmtoff=-25200
/usr/share/zoneinfo/America/Los_Angeles  Sun Nov  7 08:59:59 2010 UTC = Sun Nov  7 01:59:59 2010 PDT isdst=1 gmtoff=-25200
/usr/share/zoneinfo/America/Los_Angeles  Sun Nov  7 09:00:00 2010 UTC = Sun Nov  7 01:00:00 2010 PST isdst=0 gmtoff=-28800
  • If there are any discrepancies between the changeover dates listed on the system and the expected changeover dates, update to the latest version of tzdata with:

  • For RHEL 4:

# up2date tzdata
  • For RHEL 5 and RHEL 6:
# yum -y update tzdata

This solution is part of Red Hat’s fast-track publication program, providing a huge library of solutions that Red Hat engineers have created while supporting our customers. To give you the knowledge you need the instant it becomes available, these articles may be presented in a raw and unedited form.