DST Requires Urgent Action Why an update is necessary
Microsoft Office Outlook creates appointments and meetings using Coordinated Universal Time (UTC) format, an international standard 24-hour timekeeping system. For example, an 8 A.M. appointment on March 1, 2007, in San Francisco, California is saved as UTC 4 P.M. because DST has not yet started on March 1 and San Francisco time is 8 hours behind UTC. When a DST update is made to the Windows operating system to accommodate the new DST definitions, the computer's local time will reflect the change to DST. However, appointments made in the extended DST period will be one hour off because time changes made in Windows do not change UTC time, but rather the local time of the computer. For more information on supporting the DST changes in Windows operating systems, see KB 931836: February 2007 cumulative time zone update for Microsoft Windows operating systems. For example, when you view an appointment scheduled for 8 A.M. on March 15 in San Francisco after updating Windows but before running the Time Zone Data Update Tool, you will see a start time of 9 A.M. because it was originally stored as 4 P.M. UTC, but the local system now recognizes 4 P.M. UTC as 9 A.M. San Francisco time (4 P.M. - 8 hours + 1 for DST). What happens if you do NOT update Windows or OutlookIf you choose not to install the Windows updates and run the Time Zone Data Update Tool, then during the extended DST period, the impact on your Outlook calendar will be that appointments and reminders will appear one hour off. All-day events will shift and span two days because these events are associated with 24 specific hours rather than an individual date.
Helpful Tips to minimize the impact of the DST change Ultimately, individual calendar owners are the only ones who can validate their calendars being accurate. To minimize confusion during the DST shift, follow these simple steps:
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