The warnings recall the Year 2000, or Y2K, hysteria that reigned at the turn of the Millennium, when some worried that the computer systems that were programmed to recognize two digit years and that were used to run just about everything would suddenly stop working. But executives and enterprise IT professionals contacted by InfoWorld say that the Daylight Savings Time (DST) change, while a nuisance, is no Y2K, and they expect few disruptions to their businesses come Monday.

The new, accelerated time change is the result of the Energy Policy Act of 2005, which lengthened Daylight Savings Time in an effort to curb U.S. fuel consumption. IT vendors and industry groups recognized the potential for confusion, with many operating systems and applications programmed to use the old Daylight Savings Time date, and started warning about potential disruptions from DST just after the New Year.

In a February alert to its members, the IT ISAC (Information Sharing and Analysis Center) said that the new Daylight Savings Time could "affect all consumers from home users to large enterprises," with problems ranging from missed appointments to system failures where correct time stamps are needed to store, monitor, or operate critical infrastructures. IT-ISAC members were encouraged to identify any systems that were time dependent and request patches for affected systems.

Large platform vendors like Microsoft have also been sounding the alarm on DST in recent months, especially about the impact of the change on older versions of Windows and Microsoft Office. Windows Vista and Office 2007, released in January, are programmed to use the new DST schedule.

"We've heard a wide spectrum of comments from customers," said M3 Sweatt, chief of staff for the Windows Core Operating System Development Group. Some companies have been working on the problem since last November, when Microsoft first issued patches for Windows to address the time change. However, other firms have waited until just recently to tackle the DST change, he said.