T he odds are good that the appointments you’ve made with US or Canadian associates through Microsoft’s Exchange or IBM’s Lotus Notes or Domino are going to be off by an hour in the last three weeks of March 2007. Your legacy Java runtime environments also will likely produce incorrect time-sensitive results.
Why? Buried among the hundreds of provisions in the 1,700 pages of the United States’ Energy Policy Act of 2005 is a modest change to the rules that establish when Daylight Saving Time starts and ends. The changes, which the government ostensibly implemented as part of a federal energy conservation effort, require that beginning in 2007, Daylight Saving Time (DST) start three weeks earlier and end one week later than in previous years. (For more information on the policy’s history, see the sidebar “US Laws Governing Daylight Saving Time.”)
To stay in sync with the US, Canada and many Caribbean countries will extend their DST calendars. The European Union, however, will maintain its current DST schedule, which starts on 25 March 2007 and ends on 27 October 2007. Mexico will require some recalibration because parts of the country have adopted DST and plan to remain on the previous DST schedule (DST 2006). Countries in the Southern Hemisphere that observe DST do not synchronize their calendars to seasons in the Northern Hemisphere. Likewise, Hawaii, US territories, and the parts of Arizona that don’t observe DST won’t see any changes. For a comprehensive list of global DST start dates and times, see http://www.timeanddate.com/time/dst2007a.html.
What are the risks? Accurately tracking the local date and time can affect applications’ intended behavior. Consider how many applications in your portfolio are time sensitive. The obvious ones involve calendaring and scheduling, but the potential exposure can go much deeper. Many transaction logs (for example, ATMs) serve as the legal record of the transactions they record; being off by an hour risks legal exposure. Batch jobs set to run at midnight will now execute an hour early and truncate the first day of DST 2007 by an hour—a 23-hour computer day doesn’t pass muster in a 24-hour legal world.
Does the US DST 2007 impact only US computer users? The short answer is no. Organizations and companies with locations, customers, and users in Canada or the US might need to take corrective action. This could include not only large multinational organizations but also international banks, airlines, transportation companies, and government regulators and security agencies. With globalization, many applications and services that companies rely on might not be housed locally, where the users are; they can be located in data centers almost anywhere around the world.