More daylight-saving time means problems for developers

A pending energy bill expected to soon gain approval from the U.S. Congress means some programmers will once again need to check over their software code for potential problems handling a calendar adjustment. Congress is proposing a four-week extension of daylight-saving time (DST), a move that could trip up applications and gadgets programmed to adjust their internal clocks according to the "summer time" schedule the U.S. has kept for nearly two decades.

The IT industry will have plenty of time to prepare for the change: The extension would take effect one year after enactment of the Energy Policy Act of 2005, which likely means a 2007 start date for the new DST schedule. The energy bill won approval Tuesday in a joint U.S. Senate and House of Representatives conference committee, and is expected to soon pass the full Congress and move on to the White House.

The change would shift DST's start from April back to March and move its end from October to November. Those extra few weeks of DST will save 100,000 barrels of oil a day, according to legislators backing the change.

It will also confuse programs set to automatically handle DST hours. Summer time changes, observed in patchwork fashion around the world, have always been an annoyance for programmers and systems administrators: Online support groups are full of work-arounds and suggestions for an assortment of DST-related glitches. For example, Cisco Systems' technical support has pages of detailed technical information on solving DST problems afflicting its servers and routers, while Oracle's online discussion forum is filled with posts from developers seeking help handling esoteric DST challenges.

Many applications rely on the operating system to maintain an accurate clock, meaning Microsoft will play a critical role in keeping the world's computers running on time if DST hours change. The company says it's not worried. "We're aware of the upcoming change, and will make sure that Windows handles the transition smoothly," said Peter Houston, Microsoft's senior director of servicing strategy, in a written statement.

"Smoothly" doesn't necessarily translate to "flawlessly." Microsoft's support Web site contains dozens of articles related to DST hiccups, varying from broad problems -- some multiprocessor computers running Windows NT 4.0 Service Pack 4 or 5 have trouble adjusting to DST -- to minor oddities. In Windows Millennium Edition, the operating systems' DST adjustment accidentally reset HTML (Hypertext Markup Language) wallpaper background images to a bitmap file.

Still, no one in the industry is expecting Y2K-bug-like chaos and expense. Representatives from research firms Gartner and Forrester Research said none of their analysts are studying the impact of a DST schedule change, while several major vendors said the effects would be slight. "We view the proposed change in DST as minor," said Computer Associates International Inc. spokesman Bob Gordon. "Most of our products rely on the operating system DST determination. When the operating systems are updated to recognize the new dates, most of our products would automatically use the updated information."