Updated: Upcoming DST changes in Mexico

Article
03/08/2010

by LATAM DST Taskforce

**See updated information added on March 11 2010 at the section “Automatically changing machine time zone to a new time zone on Active Directory environments”**

Disclaimer: The information in this document is written in response to an announcement by the government of Mexico about changes in the daylight saving time in some Northern Mexico’s border cities.

The steps provided in this bulletin were created to mitigate the impacts that the daylight saving time changes will cause for customers in the affected cities. 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 Mexico that was published on 12/09/2009 is available at this location: https://gaceta.diputados.gob.mx/Gaceta/61/2009/dic/20091210-V.html

Background – Mexico DST 2010 changes

In response to a request from the citizens of some cities located on the Northern Mexico’s border the Mexican government has announced a new start and end date for the DST Schedule for 10 cities. The new dates will affect the following areas:

1) Tijuana and Mexicali, located in Baja California;

2) Juarez and Ojinaga, located Chihuahua;

3) Acuña and Piedras Negras, located in Coahuila;

4) Anahuac, located in Nuevo León;

5) Nuevo Laredo, Reynosa and Matamoros, located in Tamaulipas

The new DST schedule for these areas will be the following:

1) Daylight Saving Time begins on the second Sunday of March at 2:00AM.

2) Daylight Saving Time ends on the first Sunday of November at 2:00AM

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.

Although there will not be any hotfixes provided prior to the change on Saturday, advice and recommendations have been provided and will also be available soon on the LATAM Team Blog under the DST tag.

We understand that sometimes the governments need to change the DST schedule to attend specific needs. 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 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 parts of Mexico, 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 your location.
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: https://support.microsoft.com/kb/981128.
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.
Since KB979306 the time zone “(GMT-08:00) Tijuana, Baja California” was renamed to “(GMT-08:00) Baja California”.
Install the hotfix 981128 soon as possible.

Impacts for Outlook clients and Exchange

There is a difference between the previous DST Dates followed by the affected cities and the new dates defined by the Mexican government. We are going to call this difference “Extended DST Period” or “Delta Period”.

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

Delta periods for Mexico DST in 2010:

From Sunday, March 14^th, 2010 to Sunday, April 04^th, 2010.

From Sunday, October 31^th, 2010 to Sunday, November 07^th, 2010.

The inconvenience experienced by Outlook client users happens for all appointments during the delta periods 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.

Options to update Windows Operating Systems and correct Outlook calendars

The new DST period for the affected cities shares the same schedule with the United States. For customers that live in these cities the option is to adopt the corresponding US time zone to update the Operating Systems and Outlook calendar. The following table describes the appropriate choice:

City	Current time zone:	Change to:
Tijuana	Baja California	Pacific Time (US & Canada)
Mexicali	Baja California	Pacific Time (US & Canada)
Juarez	Chihuahua, Las Paz, Mazatlan	Mountain Time (US & Canada)
Ojinaga	Chihuahua, Las Paz, Mazatlan	Mountain Time (US & Canada)
Acuña	Guadalajara, Mexico City, Monterrey	Central Time (US & Canada)
Piedras Negras	Guadalajara, Mexico City, Monterrey	Central Time (US & Canada)
Anahuac	Guadalajara, Mexico City, Monterrey	Central Time (US & Canada)
Nuevo Laredo	Guadalajara, Mexico City, Monterrey	Central Time (US & Canada)
Reynosa	Guadalajara, Mexico City, Monterrey	Central Time (US & Canada)
Matamoros	Guadalajara, Mexico City, Monterrey	Central Time (US & Canada)

Table 1: Time zones

This section describes the anticipated impacts of this change. We recommend customers to evaluate the alternative and test before apply on their environment.

Move Machine Time Zone to new time zone

Applies to:

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

Note:

· Administrators will not be required to take any further actions when the DST ends in Mexico. Once configured on the proper time zone the machine will follow the new DST schedule.

· 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:

Item	When	Activity
1	As fast as possible, before March 14^th, 2010	Change machine time zone to the proper US time zone in Windows. This section is detailed in the “Changing Windows OS time zone”
2	As soon as operating system is updated	Adjust Outlook calendar appointments. This section is explained in ‘Adjusting Outlook calendars for users in Mexico who moved to a different time zone’’

Changing Windows OS time zone

In order to change the computer time zone to a different time zone, 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 the time zone that applies to your city (vide Table 1) and click OK:

Note: Make sure that the box ‘Automatically adjust clock for daylight saving changes’ is checked.

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. Select the time zone that applies to your city (vide Table 1) and click OK:

Note: Make sure that the box ‘Automatically adjust clock for daylight saving changes’ is checked.

Automatically changing machine time zone to a new time zone on Active Directory environments

Warning: Make sure that you only deploy this solution to machines that are located on the cities listed on this document. We recommend customers to evaluate the alternative and test before apply on their production environment.

Note: this procedure is only supported in Windows 2000, Windows XP and Windows Server 2003, Windows 7 and Windows 2008 R2 Operating Systems. Users running Windows Vista and Windows Server 2008 will have to use the procedures specified in ‘Changing Windows OS time zone to a new time zone” section.

On Active Directory environments, administrators may want to automate the change of time zones to a new time zone. 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 OS time zone’ above to move this machine to a new time zone.

Use a script to change the machine time zone to a different time zone

The script below can be used to change the current time zone to “(GMT -06:00) Central Time (US & Canada)” on the client computer. Then, the script writes an event on 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 = "Central 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 Next

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 & "." Else 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 1: In order to change the script to change the machine to a different time zone change the following line to the correspondent time zone:

a) Central time (US & Canada)

strNewTimeZone = "Central Standard Time"

b) Mountain Time (US & Canada)

strNewTimeZone = "Mountain Standard Time"

c) Pacific Time (US & Canada)

strNewTimeZone = "Pacific Standard Time"

Note 2: 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.">nul IF %errorlevel% EQU 0 GOTO SIX

cscript \\contoso.com\NETLOGON\ChangeTZ.vbs

GOTO End

:SIX ver |find /i "6.0">nul IF %errorlevel% EQU 0 GOTO End

ver |find /i "6.1">nul IF %errorlevel% EQU 0 GOTO Win7

GOTO End

:Win7

TZUTIL /G |Find /i "Central Standard Time (Mexico)" >nul IF %errorlevel% EQU 0 GOTO Central

TZUTIL /G |Find /i "Mountain Standard Time (Mexico)" >nul IF %errorlevel% EQU 0 GOTO Mountain

TZUTIL /G |Find /i "Pacific Standard Time (Mexico)" >nul IF %errorlevel% EQU 0 GOTO Pacific GOTO End

:Central TZUTIL /s "Central Standard Time" GOTO End

:Mountain TZUTIL /s "Mountain Standard Time" GOTO End

:Pacific TZUTIL /s "Pacific Standard Time"

:End

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:

ChangeTZ.cmd
ChangeTZ.vbs

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 Mexico 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:

\\contoso.com\NETLOGON\ChangeTZ.cmd

17. Click OK two times.

Adjusting Outlook calendars for users in Mexico who moved to a different time zone.

As soon as you move to a new time zone, all Outlook calendar items during the DELTA Periods (Sunday, March 14^th, 2010 to Sunday, April 04^th, 2010 and Sunday, October 31^st, 2010 to Sunday, November 7^th, 2010) will be displayed with 1 hour off.

Options to correct your Outlook calendar in this scenario:

Manually modify each appointment on the affected period (Sunday, March 14^th, 2010 to Sunday, April 04^th, 2010 and Sunday, October 31^st, 2010 to Sunday, November 7^th, 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. On the example we will change from (GMT-06:00) Guadalajara, Mexico City, Monterrey to (GMT-06:00) Central Time (US & Canada):

Download and run the installation package.
Go to Start, All Programs, Microsoft Office Outlook Tools, Time Zone Data Update Tool and Select "Permanent Time Zone Move Mode".
Properly select “(GMT -06:00) Guadalajara, Mexico City, Monterrey” from the “Original Time Zone:” drop down, and “Central Time (US & Canada)” 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.

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.

Click "OK" to correct the calendar items listed.
After moving Click “OK” again to close the tool.
Review your calendar items for the Delta Periods and verify they were correctly updated.

How to manually modify Outlook Calendar items:

After you move from another time zone, your calendar items will be one hour off on the Delta Period, from period (Sunday, March 14^th, 2010 to Sunday, April 04^th, 2010 and Sunday, October 31^st, 2010 to Sunday, November 7^th, 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. Juarez Time").
Exercise caution with the appointments and meetings in the extended DST period. When in doubt, verify the correct time with the organizer.

References:

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