A two-year-old bug in Microsoft software will finally hit this Sunday, as some software won't correctly spring ahead to the new time, as it changes to Daylight Saving Time in the US. Major problems are not expected, but some minor annoyances -- like failure of hotel wake-up call systems -- could surface. Noted cybersleuth Richard Smith, now chief technology officer of PrivacyFoundation.org, found the bug in January of 1999, but Microsoft officials say it was introduced into software back in 1995. It's a quirky bug. Basically, some Windows-based programs become confused when Daylight Savings Time kicks off on 1 April, creating an accidental April Fool's joke. For the following week, all software impacted will be one hour behind the correct time. On Sunday 8 April, the problem corrects itself. Since the bug was discovered so long ago, most systems have since been patched. But there is the possibility that so-called embedded systems, which are not networked and have no way to receive updates, might encounter the problem this weekend. In a "reminder" note to developers sent out Thursday, Smith suggested there might be pesky problems in airport arrival and departure time monitors, transportation scheduling screens, worker punch clocks or hotel wake-up systems. In other words, travelers might wake up late for church on Sunday -- and hotel desks might get some complaints from customers that wake-up calls were late. But even Smith isn't sure just how many of these problems will crop up. "My crystal ball is very fuzzy is if this bug is going to cause any problems or not," Smith said in his note. Besides, aren't people used to waking up confused on Daylight Savings Time morning? "Yes, if your wake-up system doesn't work, it's not like you needed that excuse anyway, you already have one," said Russ Cooper, who moderates a popular Windows bug mailing list. Cooper downplayed the impact of the bug, too. "Ninety-eight percent of all computers -- maybe 99 percent -- that have monitors or keyboards won't be affected," he said. The source of the problem is the way certain programs figure out what time it is. Programmers can choose to have their software ask the computer's operating system for the time, or they can ask other software to compute the time. If the program was written in using Microsoft's Visual C++, the programmer might have employed the time function in the Visual C++ Runtime Library -- and that's where the bug is. Two years ago, Smith said, there were "tons" of programs utilising the faulty clock, including Microsoft's Internet Explorer. But since then, most software has since be updated and reinstalled, and won't exhibit the bug. "It's not like desktops will have the wrong time," Cooper said. "And I can't think of a critical system that could be affected by this." Take me to ZDNet Enterprise Have your say instantly, and see what others have said. Click on the TalkBack button and go to the ZDNet News forum. Let the editors know what you think in the Mailroom. And read what others have said.