Disclaimer:  The information in this document is written in response to an announcement by the government of Chile about changes in the daylight saving time in Chile for the year of 2011.

The steps provided in this bulletin were created to mitigate the impacts that the daylight saving time changes will cause for customers in Chile. These are the impacts primarily anticipated at the time this document was written, and the effects that customers may face are not restricted to them.

The suggested actions on this document might receive additional testing. The information described in this document may change without notice.

In addition, customers should be aware that further guidance may be provided at any time by Microsoft.

Special notes: This document was revised in response to a change on the DST end date that was officially announced by the Chilean Government. We obtained this information from the following source: http://www.gob.cl/informa/2011/03/28/ministro-hinzpeter-anuncio-extension-de-horario-de-verano-en-el-pais.htm. We the official decree changing the DST dates in Chile was published by the government on the following site: http://www.horaoficial.cl/cambio.htm.

Chile DST 2011 - 2012 Start

Chilean government has announced last March (http://www.gob.cl/informa/2011/03/28/ministro-hinzpeter-anuncio-extension-de-horario-de-verano-en-el-pais.htm) a new start date for the DST period of 2011-2012:

Start of the DST Period:

For the mainland and Chilean Antarctica the Daylight saving time starts: 24:00 of the third Saturday of August the clocks should go forward to 01:00 of the next day. For the DST period of 2011-2012 the new Start date is now August 20th, 2011.

For the Easter Island and Salas y Gómez Island the Daylight saving time ends: 22:00 of the third Saturday of August the clocks should go forward to 23:00 of the same day. For the DST period of 2011-2012 the new Start date is now August 20th, 2011.

Since the new date published by the government is different from what was defined in the previous years, Windows-based computers that are not updated with one of the recently released DST updates (2543367 or 2570791) will not correctly interpret the time that is related to the transition to daylight saving time.

In addition to Microsoft products, other software, OS releases and hardware (phones, routers, switches and managed devices) may require updates and/or changes.

Our teams at Microsoft have taken several steps to alert customers and partners about the changes in Chile.

Last April Microsoft released a hotfix (2543367) to update the Windows Operating Systems with the new fallback DST date for Chile. This hotfix already contain the new start date for the DST Period 2011-2012. The most recent cumulative time zone update is available for download now. The KB2570791 was published on August 9th of 2011. The KB will be available on Windows Update on August 23rd of 2011.

Customers that followed our previous guidance (http://blogs.technet.com/b/latam/archive/2011/04/27/chile-dst-2011-fallback-update.aspx ) for the DST fallback in April and installed the KB2543367 and customer that installed the most recent cumulative update (KB2570791) are prepared for the upcoming DST start on August 20th of 2011.

We will continue to publish advice and recommendations on the LATAM Team Blog at http://blogs.technet.com/latam and at http://www.microsoft.com/chile/cambiodehora/default.aspx.

General recommendations

  • Install the cumulative update KB2570791 as soon as possible. This hotfix supersedes DST updates KB2543367, KB2443685 and KB2519231
  • This update DOES INCLUDE an update for the “UTC-04:00 Santiago” and it contains recent changes on several time zones around the world.
  • Please note that if you adjust the machine’s clock manually, you may have adverse effects on your environment. This procedure is not supported by Microsoft.
  • Contact Microsoft Support prior to any modification if you are unsure about the steps to follow in order to be prepared for the Daylight Saving Time change in Chile.
  • Microsoft product teams follow a semi-annual DST and TZ update schedule, which follows the Windows regular schedule for publishing newly legislated DST rules and time zone updates. These annual Windows "Cumulative Daylight Saving Time and Time Zone Updates" are released in December for each calendar year; a semi-annual update will be released in August/September, as needed. Microsoft products that are affected may also schedule updates to accommodate some of these changes. Some times “out-of-band” hotfixes are released to address important issues. The Microsoft Policy in Response to DST/TZ Requests can be found on the following article: http://support.microsoft.com/gp/dst_ms_response