DST Requires Urgent Action
Why an update is necessary
Steps you need to take
Tools for updating DST
Outlook Users
Frequently asked questions

Frequently asked questions (FAQs)

How is the target time zone reflected in Outlook items?
Single instance appointments and meetings are stored in UTC. The UTC time at which they are stored is determined by the computer that is creating them. In versions of Microsoft Outlook previous to Outlook 2007, there is no indication of what time zone such an appointment or meeting was created in. Outlook 2007 does store target time zone information on single instance items. Recurring appointments and meetings have the full time zone definition embedded in their data. In other words, the appointment or meeting itself understands exactly what the time zone definition and DST transition dates for it should be.

What special considerations are there for users of Windows 2000, Exchange2000 and Outlook 2000?
Due to Micorsoft's Extended Support Policy which only provides critical security patches free of charge.

The DST patches are NOT considered critical SECURITY patches by Microsoft. Organizations who possess an Extended Support Agreement, can receive hot fixes from Microsoft which will patch the Windows 2000 OS and Exchange 2000 server. According to Microsoft, the cost of an Extended Support Agreement is $4000.

Rather than spend so much on outdated technology, we recommend the following for our clients running Windows 2000, Exchange 2000, or Outlook 2000:

How does the Time Zone Data Update Tool work?
If the tool detects that there are new rules for a time zone, it can automatically attempt to transition any appointments and meetings that are affected by the change into the new version of the time zone. There are two cases:

Recurring calendar items These items have the exact time zone definition embedded in them so the tool can do a comparison of time time zone definitions and, if it matches, rewrite the appointment or meeting with the new version of the time zone information.

Single-instance calendar items These items are more complicated because, previous to Outlook 2007, they contained no time zone information. This makes it is impossible for the tool to determine whether or not the item needs updating. The tool currently assumes that any single-instance calendar item in the extended DST period were generated using the previous time zone rules and offers to update them. Since single-instance calendar items do not contain any time zone information, those items that were targeted at an unaffected time zone but happen to fall within the affected dates of the time zone being transitioned will also be identified by the tool as requiring an update. In these cases, only the appointment or meeting owner can absolutely determine whether a particular appointment should be updated.

When will my Windows time zone definitions be updated if I'm using Windows Vista?
Windows Vista already includes the new DST rules and automatically updated time zone definitions on January 1, 2007. Other Microsoft Windows operating systems will receive a DST update via Microsoft Update. For more information, see Micrososft Knowledge Base article KB 931836.

When should I run the tool?
The tool can be run manually at your discretion after the Windows time zone definitions have been updated. It is preferable to run the Outlook/Exchange tool as close as possible to the time at which the Windows time zone patch is applied (to all computers) since that will minimize the likelihood of having single-instance calendar items that were created after the Windows time zone update was applied, but before the Outlook/Exchange tool was run.

Should I run the tool if I have Outlook 2007?
Outlook 2007 has this functionality already embedded in it. You are not required to manually run the tool since Outlook 2007 automatically detects a time zone definition change and automatically prompts you to complete the update process. However, the tool contains updated enhancements that might improve your experience and is the preferred method of updating your calendar. We recommend that you cancel the dialog boxes that appear automatically in Outlook 2007 and follow the instructions to download and run the tool instead.

Which calendar items does the Time Zone Data Update Tool attempt to update?
Due to the manner in which target time zone is reflected in appointments and meetings the tool attempts to update all single-instance items that fall into the affected date ranges and all recurring appointments that have instances in the affected date ranges and were not created for other time zones. It attempts to update all such single-instance calendar items because, unless they were created in Outlook 2007 or have already been updated by a previous run of the tool, the tool cannot identify the time zone to which they are targeted.

Why doesn't the Time Zone Data Update Tool update all of my affected meetings?
The tool only updates meetings for which you are the organizer and then automatically sends updates for those meetings to all other attendees. This is required so that all meeting attendees have the correct start and end time of the meeting.

What are some situations in which I might want to run the tool multiple times?
It is a good idea to run the tool multiple times if you continue to create appointments and meetings from computers or devices that do not contain the latest daylight saving time rules. A similar situation occurs if, after running the tool, a recurring appointment or meeting that did not have any occurrences in the extended DST period is modified so that an instance now occurs within the extended DST period. The tool originally would not update the recurrences because no instances were affected by the DST changes. Now that such occurrences exist, the tool needs to be run again so that it can find and update the time zone information appropriately.

What are some situations in which I want to avoid running the tool multiple times?
If you use an Exchange account, make sure that you run the tool only from one computer at a time. Attempting to update the same calendar from multiple computers simultaneously might lead to conflicts and other problems. Due to synchronization issues, do not run the tool with your Exchange account if you are working offline. Only run the tool when connected to the server.

How does the Exchange tool compare to the Time Zone Data Update Tool?
The Exchange tool allows an Exchange administrator to apply the time zone update in silent mode to a set of selected mailboxes on the server running Exchange. Each person with an Exchange account will not have the opportunity to clear selections for appointments that do not need updating. The Exchange tool only affects calendars that are saved on the server running Exchange. Any calendars that are saved in a Personal Folders file (.pst) can only be updated by the Time Zone Data Update Tool.

What will happen to resource calendars?
Updates are sent for meetings based on the time at which the tool is run. If a room or resource is booked in two contiguous time slots and it receives the update for the later meeting that moves it back an hour first, the update will be rejected because the change would create a conflict with the first meeting. Accordingly, you should be aware of potential conflicts on shared calendars when multiple people are updating their DST rules.

What happens if I use multiple computers, not all of which are updated?
Particular attention should be made when using a combination of updated and non-updated computers. Appointments and meetings created with non-updated time zone information and viewed on an updated computer will be erroneous during three weeks in the spring (March 11, 2007, to April 1, 2007) and one week in the fall (October 28, 2007, to November 4, 2007) and you will have to re-run the tool in order to update them. And, if you have since created other single-instance appointments and meetings on the updated computer, the tool is likely to try to erroneously update them as well.

What happens if I run the tool on one of the SharePoint calendars that I'm connected to?
Connected SharePoint calendars are read-only in Outlook 2003. The Outlook/Exchange tool will incorrectly modify these calendar items on your calendar, but the updates will NOT be pushed to the SharePoint server. The two calendars will be out of synchronization. Because running the tool on a connected SharePoint calendar in Outlook 2003 is a custom action, this situation will not happen as a default case.

What about DST updates for PalmOS devices, including Treo smartphones and handhelds ?
Palm has provided device owners with a specific web page to visit to download and install updates so that they reflect the correct time when the new DST changes take effect. Without the Daylight Saving Time updates, calendar events and email messages will indicate an hour off the actual time in locations that observe DST : http://www.palm.com/us/support/downloads/dst.html

What about using computers at Home, in a Hotel Business Center, at an Internet Kiosk, or any other "public" location ?
Many customers use Microsoft Outlook Web Access (OWA) from computers outside their office network to check email and review calendar entries. Unless each and every one of these machines has been updated with the appropriate patches and updates (not likely), the time shown in the Outlook Web Access calendar view will be wrong, by one hour. Update all your home computers using these instructions to enable the correct calendar time, but assume any "public" machine you use anywhere else has not been updated. For that reason, we recommend reviewing each of your calendar appointments during the time between March 11th and April 1st and editing the subject line to include the date/time/time zone specifically, to ensure all invitees are absolutely clear about each meeting's schedule (e.g. "National Sales Meeting Conference Call - March 12th 8am PST").

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