Change in daylight-saving time could confuse some programs

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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: 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 schedule. The energy bill won approval yesterday 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 per 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 Inc.'s technical support has pages of detailed technical information on solving DST problems afflicting its servers and routers, while Oracle Corp.'s online discussion forum is filled with posts from developers seeking help handling esoteric DST challenges.

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