Outlook: Incorrect appointment times due to 2007 Daylight Saving Time change

Starting in the spring of 2007, Daylight Saving Time (DST) start and end dates for the United States will transition to comply with the Energy Policy Act of 2005. DST dates in the United States will start three weeks earlier (the second Sunday in March) and will end one week later (the first Sunday in November).

If you are an Exchange Outlook calendar user, you may see the following symptoms in your calendar that are caused by the software not "understanding" the new Daylight Saving Time start and end dates:

  • Recurring appointments that occur for the three week extended period between March 11, 2007, to April 1, 2007, AS WELL AS the one week extended period from October 28, 2007, to November 4, 2007 will be off by 1 hour.
  • During these above mentioned time times, all day events may incorrectly span a two day period, or they may lose their "all day" formatting and appear as appointments that begin at 1:00 a.m.

How can I tell if this affects me or not?
If you are an Exchange calendar user, open your calendar and look at the three week extended period between March 11 and April 1. Do you see any individual or recurring appointments that are incorrect? If you see individual appointments that are incorrect, such as a doctor appointment or meeting you have added to the calendar yourself, you can change them now to be correct with no worries that they will be altered by ITS or any external technical changes. If you see recurring meetings such as staff meetings that are incorrect for the three week extended period, yet then in April are correct again, this is the scenario ITS is working to correct using centralized administrative tools.

What is the difference between a recurring meeting and an individual meeting?
A recurring meeting can appear in your calendar daily, weekly, monthy, yearly, or however you may have configured it to continue and repeat. Examples are staff meetings, office hours, annual birthdays, or holidays. An individual meeting is one that happens once and is not configured to occur again. The distinction is important as Microsoft software places a time stamp on recurring meetings, but does not on individual meetings. The date stamp is how any update tool will "know" whether to correct the appointment for DST or not.

What is ITS planning to do?
What is ITS planning to do? ITS is testing Microsoft’s DST server-side tool against a small sub-set of ITS members. Depending on the results of the initial testing, this same server-side tool may be tested against a larger group of Outlook Exchange users from ITS.  If all goes as planned, the tool would be run against all Exchange user calendars on Saturday, March 3rd.

It is recommended that you wait for the server tool to be run to globally fix the incorrect recurring meetings in your calendar. Note that if you see any individual meetings in your calendar that are incorrect, you should fix them, as the server tool will not touch them.

What can I do now to minimize confusion?

  • Keep a shadow calendar, on paper, for the three week extended period when appointments appear incorrectly.
  • When organizing a meeting during the extended DST period, type the correct meeting time in the subject line or body of the message (for example, Project planning meeting at 8:30 a.m.) to avoid confusion, and to allow users to correct the appointment if necessary later.
  • For any meeting with multiple attendees, remember that only the meeting requestor should update the time and send the update to the other attendees.
  • If you are willing to manually fix your individual appointments, contact the ITS Help Desk to install and run the Update Tool documented below.

Is there anything I can do myself now?
Yes.  All appointments and recurring events can simply be updated manually through Outlook to reflect the correct time.

If you have a large amount of appointments or recurring events, Microsoft has released an Update Tool that you can install on your computer if you have administrative rights. The tool will fix the recurring meetings you have organized. Be aware that by default, it will also change your individual appointments by one hour.  Depending upon when the individual appointments were created this can cause them to now have the incorrect time.  It is recommended that individual appointments be manually updated through Outlook.  Events scheduled as All Day events will also need to be updated after the tool is run. See the instructions below for how to install and run the Outlook Time Zone Data Update.

How to install and run the Outlook Time Zone Data Update
You must have administrative rights on your machine to download and install this tool. If you do not have administrative rights, please contact the ITS Help Desk. Regular users can run the tool once it has been installed.

After running this tool, invitees to recurring meetings that you have arranged will receive invitations that reflect the correct time for these meetings. They will need to accept the invitations for the meeting to be updated in their calendars. Note that only the organizers of recurring meetings can fix these meetings; invitees must wait for the organizer to run the tool. Invitees must accept the invite update in order to see the change. At this time, ITS recommends that only organizers of recurring meeting affected during the extended DST time period run this tool; the server tool to be run next week should fix your calendar without having to run this tool.

The tool by default also changes individual appointments inappropriately by one hour, no matter when they were created, and you must fix these manually unless you click on the Details button as you are proceeding through the steps of the tool. This is the downside of running the client tool as opposed to waiting for the server tool to be run. The server tool will only repair your recurring meetings and leave your individual appointments alone.


  1. Log in to the computer as local administrator
  2. Launch Internet Explorer browser (Microsoft only supports their downloads via IE, not other browsers).
  3. Go to the Outlook Time Zone Data Update web page.
  4. If you see an orange-colored bar and a silver Continue button, click the Continue button and follow the prompts to Validate your copy of Windows with Microsoft. Continue to the next step. You may need to click the small, yellow warning bar if it appears at the top of the page.
  5. If you see a blue-colored bar and a silver Download button, click the Download button to download the tool.
  6. Double-click the TZMOVE.EXE file to install the tool
  7. The Change Calendar Time Zone window will open, you will be prompted to apply DST changes to any existing appointments and meetings. This is for the logged in local administrator, so click Cancel at this point
  8. Log out as local administrator
  9. Log in as the Exchange user (as you would normally log in to your Windows profile)
  10. Go to C:program filesmicrosoft officeoffice12Office Outlook Time Zone Data Update Tool and run tzmove.exe
  11. The Change Calendar Time Zone window will open
  12. The user’s full name will appear in the data file field.
  13. Click the OK button to start the tool.
  14. All calendar entries will be looked according to the rules explained in further detail with this MS KB article http://support.microsoft.com/kb/931667. This article is very helpful if you need to understand the full implications of DST changes on your calendar
  15. You can click on the Details button to display a list of all appointments to be altered. Then you can de-select any appointments that do not need to be changed, such as the individual appointments that are already correct. As they do not have time stamps, the individual appointments may appear on the list even if they do not need to be corrected.
  16. Note: To run the Outlook Zone Update tool again, browse to C:program filesmicrosoft officeoffice12Office Outlook Time Zone Data Update Tool and run tzmove.exe

Note: The Outlook DST tool can also be run on Public Folders as well as Personal Folders. Run the tool, click Custom then navigate to the folder.

More Microsoft-specific information regarding "Preparing for daylight saving time changes in 2007 " is available at: http://www.microsoft.com/windows/timezone/dst2007.mspx.