Most North American Daylight Saving Time (DST) software updates have been fairly trivial. Operating systems and time servers are easily patched to make the correct adjustments. However, many Exchange administrators are facing:

• Numerous changes in complex Knowledge Base (KB) articles.
• An unwieldy number of options for adjusting appointments with little or no guidance for selecting the best-fit option.
• A faulty tool provided by Microsoft that was fixed less than a month before DST starts.
• Uncertainty as to whether calendared appointments will be accurate, even after all of the trouble and time invested in assuring a smooth transition.

Here’s what lays in the road ahead.

Implement in Order

Microsoft tech support engineers now recommend the following order of steps, also found in KB 930879. This order contradicts earlier instructions still available as of this writing in KB 931667:

1. Install OS patch on servers (KB 931836).
2. Install OS patch on clients (KB 931836).
3. Rebase calendar appointments by applying one of these options:
   • Client-side tool. TZMove (KB 931667)/TZMove update (KB 933146). After downloading the tool and applying the hotfix, this tool can be pushed out to empower clients to rebase their own appointments. Conversely, IT may choose to run it against select client accounts.
   • Server-side tool. MsExTmz.exe (KB 930879). This tool rebases specified sets of mailboxes. It cannot be run from a system on which Exchange Server or the Exchange System Management Plug-in is installed.
   • Manual process. Apply no rebasing and instruct users to verify and adjust appointment times.
   • Some combination of the above. The MsExTmz tool can be run with a switch to adjust only recurring appointments, which Microsoft believes will be rebased properly. Users could then be instructed to verify single-instance appointments and manually adjust them.
4. Install Exchange DST patch for CDO (KB 926666). When 926666 is applied before running the rebasing tool, Outlook Web Access appointments will not be properly adjusted. Until this patch is applied, any appointments made using Outlook Web access, BlackBerry Enterprise Server, and Good Mobile devices for time/dates within the additional DST period will be incorrectly scheduled.
5. Restart Exchange.
6. Instruct users to manually correct single-instance appointments that were not moved and any other anomalies.

Note: The six-digit numbers above refer to Microsoft KB articles that provide instructions and links to the associated tools.

According to a Microsoft tech-support engineer, if 926666 was applied before using the TZMove tools, uninstall 926666, run the TZMove or Exchange Calendar Update Tool (MsExTmz.exe) as appropriate, and then reinstall 926666. Users may safely manually rebase appointments after administrators apply 926666.

Several problems may arise:

• Appointments created for dates/times within the additional DST period (three weeks in March/April, one week in October/November) before the OS was patched will be off by an hour. The TZMove tool can be run with a switch to identify and move only these appointments.
• If users have already manually rebased mis-scheduled single-instance appointments, the TZMove and MsExTmz tools will still bump them an hour, causing them to be an hour off again, creating user confusion. Either confirm that users have not manually rebased appointments, or advise accordingly.
• Each time the rebasing tool runs, it will bump single-instance appointments by an hour. Single-instance appointments created in Exchange 2003 or previous editions do not have a fixed time-reference, so rebasing tools cannot tell whether they have been adjusted or not. Recurring appointments, by nature of their coding, do not share this problem. Avoid running the rebasing tools multiple times on single-instance appointments.
• The MsExTmz tool, when run against several thousand mailboxes, may take hours or days to finish. Start now, or pursue a different process.
• Rebasing large numbers of appointments will generate appointment update alert floods that may confuse users. A switch is available for both MsExTmz and TZMove to squelch appointment update alerts. However, this switch presently cannot be used with the switch that only rebases appointments created after the OS patch was applied. Use the switch where possible.
• Beware Exchange Server slowdowns if too many users attempt to simultaneously rebase appointments involving the same resources. Enterprises with fewer than 200 users may choose to simply ride out the service slowdown. Larger enterprises may want to schedule users into timeslots to update appointments (i.e. last names A-F should update appointments from 9:00 AM to10:30 AM, and so on).

Exchange administrators may find Microsoft IT’s (MSIT) internal experience useful. Reference the MSIT section of “Preparing for Daylight Saving Time changes in 2007” for links to documents detailing Microsoft’s process for rebasing nearly 70,000 Exchange user calendars. Reference the MSIT DST Patching Overview for a sample workflow.

Like It or Not, Invoke Manual Processes to Assure Schedules

Unfortunately, Info-Tech cannot recommend that enterprises rely on Microsoft’s instructions and tools to assure all appointments are accurately adjusted. After reading Microsoft’s KB articles, it is clear that Microsoft itself isn’t sure what will happen.

In spite of following Microsoft’s new order of operations, some users report continued appointment mis-scheduling, including appointments that are still an hour off when viewed from Outlook, but correct when viewed through Outlook Web Access. At this late point in the game, such problems are essentially unresolvable without applying manual processes after the DST start date.

Whether relying on users to manually rebase all appointments or just to rebase single-instance appointments, IT will need to supply guidance. Provide the following instructions to end-users:

1. Print out a copy of your calendar by Friday, March 9^th. Be sure to print both affected date ranges of March 11 to April 1 and October 28 to November 4.
2. Manually verify and update your appointments on Monday, March 11.
3. If IT does not run MsExTmz on recurring appointments, include this further user instruction. Send fresh invitations for recurring appointments and then delete the original appointment instead of adjusting the time on the original recurring appointment.

Bottom Line

Preparing Exchange 2003 for DST rules for 2007 should have been quite simple. Instead, Microsoft Exchange administrators are awash in uncertainty, alarm, and confusion.  There is no magic pill. Follow this advice to mitigate as much frustration as possible.