Guidance for Chile DST Changes effective Saturday, March 13, 2010

by LATAM DST Taskforce

**See updated information added on March 11 2010 at the section ‘(GMT -04:00) Santiago’ time zone in Windows 2000 Operating Systems **

DisclaimerThe 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 2010.

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 will be provided at any time by Microsoft.

Special notes: The official decree changing the DST dates in Chile is published by the government on the following site:


Background – Chile DST 2010 changes

In response to the recent natural disaster that impacted the country the Chilean government has announced a new end date for the DST period of 2009-2010. The new fallback information is the following:

For the mainland and Chilean Antarctica the Daylight saving time ends: 24:00 of April 3rd, 2010 the clocks should go back to 23:00 of the same day.

For the Easter Island and Salas y Gómez Island the Daylight saving time ends: 24:00 of April 3rd, 2010 the clocks should go back to 23:00 of the same day.

Since the new date published by the government is different from what was defined in the previous years, Windows-based computers will not correctly interpret the time that is related to the transition to daylight savings time.

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

Microsoft is released a hotfix to address the changes. The hotfix 981128 updates the DST end date for the “(UTC-04:00) Santiago”.

For Windows 2000 machines, the hotfix KB 981128 will only be available for customers with Extended Hotfix Agreement (EHA). Customers with no EHA can update their Windows 2000 systems via ‘Updating ‘(GMT -04:00) Santiago’ time zone in Windows 2000 Operating Systems’ section in this document.

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

This document describes the steps that need to be done to prepare your machines for the upcoming changes.

We will publish advice and recommendations on the LATAM Team Blog at and at

We understand the hardship that the Chilean people are facing at this moment but a few days is a tough timeframe to get everyone alerted to a change of this magnitude. In order to achieve more seamless transitions to new DST rules and time zones, ample advance notice and concentrated efforts on promoting any change should be provided to the people and businesses impacted. Microsoft recommends a minimum timeframe of 6 months to an ideal 1 to 1½ year advance notification.


General recommendations

  • The most recent cumulative update to daylight saving time (DST) and world time zones (TZ) is now available for supported versions of the Windows Operating System via Microsoft Download Center and Windows Update. For more information about this cumulative DST and TZ update, visit the following Microsoft Web site:
  • 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, 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.
  • Hotfix 981128 supersedes DST update 979306.
  • Install the hotfix 981128 soon as possible.
  • 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.
  • Before applying the hotfix on Windows Operating Systems to reflect the change in Daylight Saving Time in Chile, be aware of potential issues that will affect Microsoft Office Outlook and Exchange Server. Read “Impacts for Outlook clients and Exchange” section for more details.
  • 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.


Impacts for Outlook clients and Exchange


There is a difference between the DST Dates established in 2008-2009 and the new date defined by the Chilean government for 2010.  We are going to call this difference “Extended DST Period” or “Delta Period”.

For the year 2010, we have a delta period at the end of the DST as follows:

Delta period for Chile DST in 2010:


From Saturday, March 13th, 2010 to Saturday, April 03rd, 2010.

The inconvenience experienced by Outlook client users happens for all appointments during the delta period that were created before the administrators update the DST dates on the operating system.

Those appointments will be off 1 hour. This may happen for both recurring and single-instance appointments.

The appointments created after the DST dates have been updated on the operating system will have the correct time.

Why do we experience this behavior?

To answer this question, we need to understand how Outlook schedule meetings and appointments:

Three factors affect the scheduling of a meeting and appointment in Outlook:

  • The computer’s clock setting (time).
  • The computer’s local time zone setting.
  • The computer’s daylight saving time adjustment setting.

Outlook time stamps the message request with the Greenwich Mean Time for the meeting. Outlook calculates Greenwich Mean Time by using the computer’s clock time, plus or minus the local time zone adjustment, minus (depending upon the time of year) the daylight-saving time adjustment.

As soon as Outlook receives the meeting request it will calculate the meeting time for the recipient and schedule it on the calendar. If any of the three factors listed earlier are incorrect at that time, the meeting time will be incorrect. You cannot correct the time after the fact by correcting the factor in error; you must open the meeting request and manually correct the scheduled time.

How to update Windows Operating Systems and correct Outlook calendars

Customer needs to follow the steps bellow to update the Operating Systems and Outlook calendar.

This section describes the anticipated impacts of the changes. We recommend customers to evaluate steps before apply on their environment.


Applies to:

  • Windows XP, Windows 2003, Windows Vista, Windows 7, Windows Server 2008 and Windows Server 2008 R2 users

The following graph shows a summary of tasks associated with this change:


Below is a brief description of these activities:





As fast as possible, starting Saturday March 6th 2010

Install the hotfix 981128


As soon as operating system is updated

Adjust Outlook calendar appointments. This section is explained in ‘Adjusting Outlook calendars for users in Chile after apply the hotfix.

Updating ‘(GMT -04:00) Santiago’ time zone in Windows 2000 Operating Systems

Note:     This section is based on the following article:
914387 – How to configure daylight saving time for Microsoft Windows operating systems

1. Create a registry file that contains the new DST settings for Chile following these steps below:

1.1. Click Start, click Run, type notepad, and then click OK.

1.2. Copy the following registry information, and then paste it into the Notepad document:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones\Pacific SA Standard Time]
"Display"="(GMT-04:00) Santiago"
"Dlt"="Pacific SA Daylight Time"
"Std"="Pacific SA Standard Time"

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones\Pacific SA Standard Time\Dynamic DST]

1.3. On the File menu, click Save As.

1.4. Select a destination, and then type TZupdate.reg in the File name box. 

1.5. In the Save as type box, click All Files, and then click Save.

2. Import this registry key on target machines by double clicking in the TZupdate.reg and clicking ‘Yes’ when prompted. All machines (clients and servers) must be updated with this registry information.

3. In order to deploy these time zone changes in a corporate environment, you can use a startup script as described in the session “Deploy the registry file with the new DST information using Group Policy” below.

Note:     The registry settings above contain the following information for the “(GMT -04:00) Santiago” time zone:
Daylight saving time begins: 2nd Saturday of October at 23:59:59.999 local standard time
Daylight saving time ends:
1st Saturday of April, 2010 at 23:59:59.999 local daylight saving time

Use a script to reload the TimeZoneInformation registry key

Time zone information is stored in two locations. We need to make sure these locations are updated. Importing the TZupdate.reg file updates the time zone database in the registry. Next, you must create a script that updates the time zone information registry key in the CurrentControlSet. You can deploy this script by using Group Policy or another deployment mechanism.

The script identifies the current time zone of the client computer and then reloads the Time Zone Information registry key with the updated information from the time zone database. Then, the script writes an event to the Application log of the client computer where the script was run.

  1. Click Start, click Run, type notepad, and then press ENTER.
  2. Copy the following code, and then paste it into the Notepad document:

    Set objSh = CreateObject("WScript.Shell")

    ‘Get the StandardName key of the current time zone
    szStandardName = objSh.RegRead("HKLM\SYSTEM\CurrentControlSet\Control\TimeZoneInformation\StandardName")

    ‘Enumerate the subkeys in the time zone database
    const HKEY_LOCAL_MACHINE = &H80000002

    Set objReg=GetObject("winmgmts:{impersonationLevel=impersonate}!\\.\root\default:StdRegProv")
    szTzsKeyPath = "SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones"
    objReg.EnumKey HKEY_LOCAL_MACHINE, szTzsKeyPath, arrTzSubKeys

    ‘Step through the time zones to find the matching Standard Name
    szTzKey = "<Unknown>"
    For Each subkey In arrTzSubKeys
    If (objSh.RegRead("HKLM\" & szTzsKeyPath & "\" & subkey & "\Std") = szStandardName) Then
    ‘Found matching StandardName, now store this time zone key name
    szTzKey = subkey
    End If

    If szTzKey = "<Unknown>" Then
    ‘Write entry to the Application event log stating that the update has failed to execute
    objSh.LogEvent 1, "Chile DST 2009-2010 Registry Update and Refresh failed to execute on this computer. Time zones failed to enumerate properly or matching time zone not found."
    Wscript.Quit 0
    End If

    Dim process, processid, result, strUpdateCommand
    Set process = GetObject("winmgmts:{impersonationLevel=impersonate}!\\.\root\cimv2:Win32_process")

    ‘Add time change privilege to the process object
    process.Security_.Privileges.AddAsString "SeSystemTimePrivilege",True
    strUpdateCommand = "control.exe timedate.cpl,,/Z" & szTzKey

    ‘Launch control.exe to refresh time zone information using the TZ key name obtained above
    result = process.create(strUpdateCommand,Null,Null,processid)

    If result <> 0 Then
    objSh.LogEvent 1, "Chile DST
    2009-2010 Registry Update and Refresh failed to execute on this computer. Unable to refresh the Timezone database."
    Wscript.Quit 0
    End If

    ‘Get current display name of refreshed time zone
    szCurrDispName = objSh.RegRead("HKLM\" & szTzsKeyPath & "\" & szTzKey & "\Display")

    ‘Write entry to the Application event log stating that the update has executed
    objSh.LogEvent 4, "Chile DST 2009-2010 Registry Update and Refresh has been executed on this computer." & chr(13) & chr(10) & chr(13) & chr(10) & "Current time zone is: " & szCurrDispName & "."

  3. On the File menu, click Save As.
  4. Select a destination, and then type “refreshTZinfo.vbs” in the File name box.
  5. In the Save as type box, click All Files, and then click Save.
  6. Double click in the refreshTZinfo.vbs to refresh time zone information.

Note: Microsoft provides programming examples for illustration only, without warranty either expressed or implied. This includes, but is not limited to, the implied warranties of merchantability or fitness for a particular purpose. This article assumes that you are familiar with the programming language that is being demonstrated and with the tools that are used to create and to debug procedures. Microsoft support engineers can help explain the functionality of a particular procedure. However, they will not modify these examples to provide added functionality or construct procedures to meet your specific requirements.

Deploying DST modifications using Group Policy
  1. Click Start, click Run, type notepad, and then press ENTER. 
  2. Copy the following code, and then paste it into the Notepad document.

    @echo off

    regedit /s \\\NETLOGON\TZupdate.reg
    ver |find /i "6.0">nul
    IF %errorlevel% EQU 0 GOTO end
    cscript \\\NETLOGON\refreshTZinfo.vbs


    Note: You must replace the \\ notation above with the actual DNS domain name for your Active Directory domain.
  3. On the File menu, click Save As.
  4. DST2010Update.cmd in the File name box.
  5. In the Save as type box, click All Files, and then click Save.
  6. Copy the following files to the Netlogon share folder of the domain controller that holds the PDC emulator role in the domain:


  7. Wait until Active Directory replication occurs. Also, wait until the files and folders in the system volume (SYSVOL) shared folder replicate to domain controllers in the domain.
  8. Click Start, click Run, type control admintools, and then click OK.
  9. Double-click Active Directory Users and Computers.
  10. Select an Organizational Unit (OU) which contains the computers that you want to apply this script to. In this example, we will use an OU that is named DST-COMPUTERS. This example also assumes that this OU contains computer accounts.
  11. Right-click the DST-COMPUTERS OU and then click Properties.
  12. Click the Group Policy tab, click New, type DST Registry Update, and then press ENTER.
  13. Click Edit. The Group Policy Object Editor tool starts.
  14. Expand Computer Configuration, expand Windows Settings, and then click Scripts (Startup/Shutdown).
  15. Double-click Startup, and then click Add.
  16. In the Script Name box, type the universal naming convention (UNC) path of the DST2010Update.cmd file that is located in the Netlogon share. For example, type \\\NETLOGON\DST2010Update.cmd
  17. 17. Click OK two times. 

Note: Client computers that are within the DST-COMPUTERS organizational unit will run the startup script the next time the machine starts up, meaning all machines needs to be restarted to be able to recognize the new DST configuration via Startup script.

Important information about procedures described in this section:
  • The instructions above can be applied on Windows 2000, Windows XP and Windows Server 2003 Operating systems, however after performing these instructions on a Windows 2003 operating system; the current time zone may not be updated. In this case you may need to restart the machine or run the refreshTZinfo.vbs script manually.

  • The manual instructions above are not supported on Windows 7, Windows Server 2008 R2, Windows Server 2008, and Windows Vista operating systems. Customers using Windows 7, Windows 2008 R2, Windows Server 2008 and Windows Vista must install hotfix KB 981128 to update their systems.

Adjusting Outlook calendars for users in Chile after apply the hotfix

As soon as you apply the hotfix, all Outlook calendar items from Saturday, March 13th, 2010 to Saturday, April 03rd, 2010, will be displayed 1 hour off.

Options to correct your Outlook calendar in this scenario:

  • Manually modify each appointment on the affected period (Saturday, March 13th, 2010 to Saturday, April 03rd, 2010) after the operating system time zone has been changed. Instructions on the section “How to manually modify Outlook Calendar items”

– or –

  • Another option is to use the "Exchange Calendar Update tool" to correct the Outlook calendar items. This procedure is discussed on the section “How to use “Exchange Calendar Update Tool” after a time zone update”

– or –

  • Customers may also opt to use the "Outlook Time Zone Data Update Tool version 3.0" to correct the Outlook calendar items. This procedure is explained below.

Special note:

We recommend you to print your calendar before any changes are made, and then review the calendar items to make sure these items appear at the correct times. You can use this printed copy of the calendar items to verify that Outlook has been updated successfully.

Step by step procedure to use “Outlook Time Zone Data Update Tool version 3.0” after a time zone move

The following describes the steps to be followed by end-users performing a time zone move:

  1. The steps below can be followed for users who applied the hotfix
  2. Go to Start, All Programs, Microsoft Office Outlook Tools, Time Zone Data Update Tool and Select "Permanent Time Zone Move Mode".
  3. Properly select “(GMT -04:00) Santiago” from the “Original Time Zone:” drop down, and “(GMT -04:00) Santiago (Update)” for the “New Time Zone:” drop down and click OK.
    NOTE: As with standard time zone updates, the tool defaults to updating affected items on your Calendar and in your Reminders folder.  If you would like to update additional items (e.g. items in additional Calendars or a PST), you can do so by clicking the ‘Custom…’ button and manually selecting the target folder.
  4. The tool will inspect your mailbox and will report how many appointments will be moved:
    If you click “Details” the appointment list will appear and you will be able to select all (default) or some of the appointments. In a normal situation you will move all the appointments to the new time zone. Click “OK” in the following dialog to proceed moving the appointments. A log file “Outlook Time Zone Update .log” will be generated in the %temp% directory.
  5. Click "OK" to correct the calendar items listed.
  6. After moving Click “OK” again to close the tool.
  7. Review your calendar items from Saturday, March 13th, 2010 to Saturday, April 03rd, 2010 and verify they were correctly updated.


How to manually modify Outlook Calendar items:

After you apply the hotfix your calendar items will be one hour off on the Delta Period, from Saturday, March 13th, 2010 to Saturday, April 03rd, 2010.

A simpler alternative to correct the Outlook Calendar items is by adjusting the appointments manually. To do so, please proceed as follows:

  1. Start Outlook, and then open the Outlook calendar.
  2. Manually move each meeting that you organized so that they occur at the correct time.
  3. Send an update for each meeting that you moved to the meeting attendees. This action causes the calendar for each attendee to display the correct time for the meeting.
  4. Manually move each single-instance appointment.
  5. Manually move all recurring appointments that occur in the extended DST period.


How to use “Exchange Calendar Update Tool” after a time zone update:

You may use the “Microsoft Exchange Calendar Update Configuration Tool”. This tool allows administrators to move the appointments of all users in a centralized way.

We should note however, that running this tool is a complex procedure, recommended only for organizations in which the Outlook tool is not suitable.

Depending on several factors, described on the article below, you may need to run the “Outlook Time Zone Update Tool” for certain users.

Instructions on how to use the "Exchange Calendar tool" can be found on the article KB 941018.

941018 How to address daylight saving time by using the Exchange Calendar Update Tool



Where can I find step-by-step instructions on how to use the rebasing tools?

  • Step by step instructions on how to use the Outlook Time Zone Data Update 3.0 can be found here.

  • Step by step instructions on how to use the Exchange Calendar Update tool can be found here.


Recommendations to minimize the impacts on Outlook/Exchange:

  • Simulate the changes on a lab environment, so you know what will happen and what to expect.
  • Work in conjunction with the operating system team to update the DST dates as soon as possible to minimize the chance of users creating new appointments during the delta period before the operating system DST dates get updated.
  • Before doing any change on the DST information, request the users to print their schedule so they have a reference to follow in order to manually update the appointments later if needed.
  • Take a full online backup of your Exchange Servers in case you decide to use the Exchange Calendar Update Tool.
  • For the meetings with multiple attendees only the meeting requestor should update the time and send the update to the others.
  • Include the time of the meeting in the e-mail request so that invitees can double check the correct meeting time (such as, "Project brainstorming – 11:00 A.M. Santiago Time").
  • Exercise caution with the appointments and meetings in the extended DST period. When in doubt, verify the correct time with the organizer.



941018 How to address daylight saving time by using the Exchange Calendar Update Tool

931667 How to address time zone changes by using the Time Zone Data Update Tool for Microsoft Office Outlook

943390 Some Outlook calendar items are rebased incorrectly when you use the Outlook Time Zone Data Update Tool to adjust for daylight saving time changes in certain time zones

934001 A troubleshooting guide to the Exchange Calendar Update Tool (Msextmz.exe)

Comments (2)

  1. rodrigo says:

    Hello Guys

    What about MS Sharepoint Services 3.0 I have updated DST for the OS server but in Sharepoint still remains old DST.

    Please your help!

  2. Latam says:

    Hello Rodrigo,

    We have a blog post the describes how to address DST issues on SharePoint:

    You can also check the KB888253 – "How to manually update the DST period for a time zone definition in Windows SharePoint Services by modifying the Timezone.xml file ":;EN-US;888253

    Best regards,