Patsy Franklin

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What’s new with tzdata: The time zone database for Red Hat Enterprise Linux

What’s new with tzdata: The time zone database for Red Hat Enterprise Linux

The Time Zone Database (tzdata) provides Red Hat Enterprise Linux (RHEL) with data that is specific to the local time zone. Applications in the Linux operating system use this data for various purposes. For instance, the GNU C Library (glibc) uses tzdata to ensure APIs such as strftime() work correctly, while applications such as /usr/bin/date use it to print the local date.

The tzdata package contains data files documenting both current and historic transitions for various time zones around the world. This data represents changes required by local government bodies or by time zone boundary changes, as well as changes to coordinated universal time (UTC) offsets and daylight saving time (DST).

This article is a quick update about changes to the tzdata package in 2019, as well as possible time zone changes that we are monitoring for package updates in 2020.

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Time zone data (tzdata): 2018 data format changes and Red Hat Enterprise Linux

Time zone data (tzdata): 2018 data format changes and Red Hat Enterprise Linux

Red Hat Enterprise Linux (RHEL) needs time zone information in order for all applications in the operating system to correctly print local time. The GNU C Library (glibc) makes use of the tzdata package in order to make APIs such as strftime() work correctly, while applications such as /usr/bin/date make use of this information to print the local date.

The tzdata package contains the data files documenting both current and historic transitions for various time zones around the world. This data represents changes required by local government bodies or by time zone boundary changes, as well as changes to UTC offsets and daylight saving time (DST).

This article describes three variants of the tzdata time zone data format that were introduced in 2018 and how tzdata changes will be made in Red Hat Enterprise Linux.

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Review of tzdata Updates for 2015

The tzdata package includes data files documenting current and historic time zone transitions. Red Hat picks up tzdata updates within 24 hours of an upstream release. We modify the packaging files to pick up the new time zone
transitions and thoroughly test to verify any changes prior to releasing on RHEL 4, 5, 6, and 7. For more information on this process see: https://developers.redhat.com/blog/2014/11/12/time-zone-data-tzdata-changes-redhat-updates/

2015 included several updates to tzdata, not the least of which was the addition of a new leap second. When we look at time zone changes, we refer to the effective date. This is the date that the change will occur. The leap second effective date was June 30, 2015 but the code to implement the change was well documented in IERS Bulletin C 49 which allowed us to release the update in February, well in advance of the effective change. Despite some initial concerns about the impact the change might have, the transition appeared to pass without any significant issues.

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