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:

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.

In some cases, time zone changes were announced with very little preparation time before the effective date. In April we shipped two tzdata updates within 11 days of each other. tzdata-2015c was shipped on April 17 with an update to move Egypt's spring DST transition one week forward to April 30th. Shortly after tzdata-2015c was shipped, the Egyptian Government announced that it would cancel DST for 2015. This change was apparently related to low energy costs reducing the energy consumption benefits of DST. As a result of this announcement, tzdata-2015d was shipped on April 28, 2015.

Another example of a last minute time zone change involved Morocco. Morocco usually suspends DST during Ramadan. The dates for Ramadan vary from year-to-year requiring an annual update to tzdata. In 2015, the Moroccan Government announcement of the DST suspension date was so close to the effective date that we were forced to create a patched version of tzdata in advance of the upstream release for customers who required the update before the upstream update was ready. Once the upstream update was released, we rebased to the upstream tzdata-2015e update.

Several other locations required DST related tzdata updates as well, including Turkey, Palestine, Mongolia and Fiji.

A note-worthy change not related to DST was North Korea's decision to celebrated the anniversary of it's liberation from Japan by changing their time zone from GMT+9 to GMT+830.

In all, there were seven releases of tzdata in 2015 impacting many parts of the world.

Last updated: April 6, 2018