Upcoming DST changes in Chile


by LATAM DST Taskforce

**This post contains outdated information and has been superseded by a new post, please review updated information here**


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 not yet published by the government on the following site: http://www.horaoficial.cl/ thus the information on this bulletin may not be accurate. We are releasing this information as a preventive measure. The official site of the Chilean Government mentions the probable change: http://www.gobiernodechile.cl/viewNoticia.aspx?idArticulo=30098

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: 22:00 of April 3rd, 2010 the clocks should go back to 21:00 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 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 to the change in Chile.

At this moment Microsoft is working on a hotfix to update the Windows Operating Systems with the new fallback DST date for Chile. All the efforts are being made to have the hotfix ready before the March 13rd 2010. Before release a hotfix Microsoft needs to follow test procedures to minimize the possibility of any adverse effect. We cannot guarantee that the hotfix will be released before the change.

This document describes the supported workaround that needs to be followed if the hotfix is not provided prior to the change on Saturday March 13rd. Customers that follow this guide will need to change back to the proper time zone as soon as the hotfix is available.

When the hotfix is released we will publish advice and recommendations on the LATAM Team Blog at http://blogs.technet.com/latam and at http://www.microsoft.com/argentina/dst.

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

§ Please keep monitoring the sites http://blogs.technet.com/latam and at http://www.microsoft.com/argentina/dst to know when the hotfix is released.

§ Install the hotfix as soon as it is available. If you follow this guide you will need to change the computers back to “GMT-04:00 Santiago” after apply the hotfix.

§ 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 changes 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.

§ 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: http://support.microsoft.com/kb/979306.

§ This update does not include any update for the “GMT-04:00 Santiago” but it contains recent changes on several time zones around the world.

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

Applies to:

· Windows 2000, Windows XP, Windows 2003, Windows Vista, Windows 7, Windows Server 2008 and Windows Server 2008 R2 users


· Administrators will be required to take further actions when the DST ends in Chile, next April 3rd 2010. A fallback procedure to the correct time zone needs to be applied.

· There is no automatic way of changing the time zone on Windows Vista, Windows 2008, Windows 7 and Windows 2008 R2 machines. This change has to be done manually.

· Administrators will not be able to correct calendar items in a centralized way (directly on the Exchange Server).

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

Change machine time zone to ‘(GMT -3:00) Cayenne, Fortaleza’ in Windows. This section is detailed in the “Changing Windows OS time zone to ‘(GMT -3:00) Cayenne, Fortaleza’”


As soon as operating system is updated

Adjust Outlook calendar appointments. This section is explained in ‘Adjusting Outlook calendars for users in Chile who moved to '(GMT -03:00) Cayenne, Fortaleza’’


April 03th, 2010

Period that users will have to change computer time zone back to ‘(GMT -4:00) Santiago’ and readjust Outlook calendar appointments to the new time zone definition.


Changing Windows OS time zone to ‘(GMT -3:00) Cayenne, Fortaleza’

In order to change the computer time zone to ‘(GMT -3:00) Cayenne, Fortaleza’, please follow the steps below:

For Windows Vista, Windows Server 2008, Windows 7 and Windows 2008 R2 machines:

1. Click Start and type:  control timedate.cpl

2. Click ‘Change time zone…’ button:


3. Select ‘(GMT 03:00) Cayenne, Fortaleza’ and click OK:


Note: If your machine does not have the KB979306 applied the display name will be UTC-03:00 Cayenne.

For Windows 2000, Windows XP and Windows Server 2003 machines:

1. Click Start button, select ‘Run’ and type the following command:
control timedate.cpl

2. Click ‘Time Zone’ tab and select ‘(GMT -03:00) Cayenne, Fortaleza’:


Note: If your machine does not have the KB979306 applied the display name will be GMT-03:00 Cayenne.

Automatically changing machine time zone to ‘(GMT -3:00) Cayenne, Fortaleza’ on Active Directory environments

Warning: this procedure is only supported in Windows 2000, Windows XP and Windows Server 2003 Operating Systems. Users running Windows Vista, Windows Server 2008, Windows 7 or Windows 2008 R2 will have to use the procedures specified in ‘Changing Windows OS time zone to ‘(GMT -3:00) Cayenne, Fortaleza’’ section.

On Active Directory environments, administrators may want to automate the change of time zones to ‘(GMT -03:00) Cayenne, Fortaleza’. This section explains how to deploy this time zone change via startup script. These procedures need to be executed in a Domain Controller or another machine with Admin Tools installed.

After performing all the steps below, all machines need to be restarted to automatically change the computer time zone. To avoid restarting a specific machine, please execute the procedures ‘Changing Windows PC Operating Systems time zone’ above to move this machine to ‘(GMT -03:00) Cayenne, Fortaleza’ time zone.

Use a script to change the machine time zone to (GMT -03:00) Cayenne, Fortaleza

The script below can be used to change the current time zone to (GMT -03:00) Cayenne, Fortaleza of the client computer. 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.

On Error Resume Next
strNewTimeZone = "SA Eastern Standard Time"
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
szCurrentTzKey = "<Unknown>"
For Each subkey In arrTzSubKeys
      strTimeZoneStandarName = ""
      strTimeZoneStandarName = objSh.RegRead("HKLM\" & szTzsKeyPath & "\" & subkey & "\Std")
    If (strTimeZoneStandarName = szStandardName) Then
        'Found matching StandardName, now store this time zone key name
        szCurrentTzKey = subkey
    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" & strNewTimeZone

'Launch control.exe to change time zone using the TZ key name stored in strNewTimeZone
result = process.Create(strUpdateCommand, Null, Null, processid)
If result <> 0 Then
    objSh.LogEvent 1, "Process to change machine time zone failed to execute on this computer. Unable to change machine time zone."
    wScript.Quit 0
End If

'Get the display name from previous time zone and compare with the new time zone
szPrevDispName = objSh.RegRead("HKLM\" & szTzsKeyPath & "\" & szCurrentTzKey & "\Display")
szNewDispName = objSh.RegRead("HKLM\" & szTzsKeyPath & "\" & strNewTimeZone & "\Display")

'Write entry to the Application event log stating that the update has executed
If szPrevDispName = szNewDispName Then
    objSh.LogEvent 4, "Machine time zone was refreshed. The current time zone is: " & Chr(13) & Chr(10) & Chr(13) & Chr(10) & szNewDispName & "."
    objSh.LogEvent 4, "Machine time zone was changed from: " & Chr(13) & Chr(10) & Chr(13) & Chr(10) & szPrevDispName & Chr(13) & Chr(10) & Chr(13) & Chr(10) & "To: " & Chr(13) & Chr(10) & Chr(13) & Chr(10) & szNewDispName & "."
End If

3. On the File menu, click Save As.

4. Select a destination, and then type “ChangeTZ.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 ChangeTZ.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 time zone changes using Group Policy

1. Click Start, click Run, type notepad, and then press ENTER. 

2. Copy the following lines, and then paste it into the Notepad document.

@echo off
ver |find /i "6.0">nul
IF %errorlevel% EQU 0 GOTO end
cscript \\contoso.com\NETLOGON\ChangeTZ.vbs

Note:     You must replace the \\contoso.com notation above with the actual DNS domain name for your Active Directory domain.

3.    On the File menu, click Save As.

4.    Select a destination, and then type ChangeTZ.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 Sites and Services. 

10.    Select a site where the computers in Chile are located. (Small environments may have only a site named ‘Default-First-Site-Name’).

11.    Right-click this site, and then click ‘Properties’.

12.    Click the Group Policy tab, click New, type DST Time Zone Change, 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 ChangeTZ.cmd file that is located in the Netlogon share. For example, type:


17.    Click OK two times.

Adjusting Outlook calendars for users in Chile who moved to '(GMT -03:00) Cayenne, Fortaleza’

As soon as you move to the time zone '(GMT -03:00) Cayenne, Fortaleza", 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 -

  • Customers may also opt to use the "Outlook Time Zone Data Update Tool version 3.0" on the mode Permanent Time Zone Move 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 changed their time zone configuration to “(GMT -03:00) Cayenne, Fortaleza”.

2. Download and run the installation package from:

3. Go to Start, All Programs, Microsoft Office Outlook Tools, Time Zone Data Update Tool and Select "Permanent Time Zone Move Mode".

4. Properly select “(GMT -04:00) Santiago” from the “Original Time Zone:” drop down, and “(GMT -03:00) Cayenne, Fortaleza” 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.

5. 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.

6. Click "OK" to correct the calendar items listed.

7. After moving Click “OK” again to close the tool.

8. 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 move from another time zone to '(GMT -03:00) Cayenne, Fortaleza", 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.

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

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

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

Comments (2)

  1. Anonymous says:

    Hello Microsoft.

    I am wondering if your are on track for March 13rd 2010 ?

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