Wednesday, February 07, 2007

Get Ready for Daylight Savings Time 2007

Does your application use a table that lists the date and time of the switch to/from Daylight Savings time? If so, be forwarned: Congress has changed the dates in the United States beginning in 2007! Canada and many Carribean countries have changed their DST timetables as well.

Previous start to DST: First Sunday of April (1 April 2007)
New start of DST: Second Sunday of March (11 March 2007)
Previous end of DST: last Sunday of October (28 October 2007)
New end of DST: first Sunday of November (4 November 2007)

What types of applications could be afected?

Scheduling Applications. The most obvious are calendaring or scheduling applications, especially those that accomodate multiple international time zones. One example might be an international air freight scheduling system. Another example would be CRM scheduling systems that send email notices that localize the time of a scheduled appointment.

Applications with Time Calculations. An application that performs calculations using minutes or hours could be thrown off. For example, piece workers who are paid bonuses based on exceeding a certain number of pieces in a given time period. The calculations could be off by 60 minutes or 1 hour.

Data Synchronization Batch Jobs Suppose one data center is scheduled to synchronize data at a given local time, say 2 am, and another data center is normally completing its batch jobs prior to that so that the synched data center has current information -- or at least they should have, but the foreign data center does not know that it is synchronizing to data that has not yet updated because of the time change. Since it is a batch job that has not completed, the information could be off by a complete 24 hours or more. Any reports generated against that information, or supply chain orders dependent on that information, could be seriously off.

Planes Will Not Fall Out of the Sky I talked to my colleagues about this and they reminded me that planes will not fall out of the sky. But it is worth considering now, whether any of your applications are dependent on accurate update of daylight savings time.