February 12, 2007 By Gina M. Scott
The problem is that programs like Microsoft Outlook are programmed to make the time switch on the traditional April and October dates. So when the changes are made according to the new DST schedule, programs that depend on a computer's internal clock-calendaring and scheduling applications, for example-won't align with real time.
In addition, many calendaring applications don't simply use the computer clock; they often set their own time flags to facilitate scheduling in multiple time zones. Simply adjusting the computer clock will cause an appointment that was coded for Eastern Standard Time to show up one hour off after the computer clock is updated with the new DST schedule.
If only the computer clock is updated and not the corresponding calendar items, appointments in the changed DST window for this year and future years are all impacted by one hour.
There could also be complications in applications that use time stamped data. Patches should be applied to applications or application environments to make sure that they will correctly handle the new daylight saving time rules.
The Multi-State Information Sharing and Analysis Center (MS-ISAC) released recommendations for dealing with this issue:
The DST issue goes beyond desktop computer systems and extends to things like mobile phones, security systems, and environmental controls. Modern buildings use computerized heating and cooling and access control that are often programmed around typical working hours, for example to unlock entrances, turn on lighting, or adjust heating. Another example might be sophisticated logistics systems that track just-in-time manufacturing processes into a state where parts deliveries may no longer align with workers' scheduled shifts.