Windows to Stumble on Daylight-Saving Time

Microsoft acknowledges bug that will make your PC report the time incorrectly in 2001.

Andrew Brandt, PC World

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If it's not corrected, the "April Fool's 2001 Bug" will cause a multitude of applications not to take daylight-saving time into account during the week of April 1 though 7, 2001.

Microsoft is aware of the problem and has eliminated it in a yet-unreleased developer's tool and in early beta versions of Windows 2000. The bug's effect may be minor irritation, but it will affect a wide variety of Windows applications.

Count Not the Hours

The bug exists in Microsoft's Visual C++ Runtime Library, a file installed by Windows and several Windows-based applications. It affects only applications that use the Library to determine the time of day--which includes both the Internet Explorer and Netscape Communicator Web browsers, among many other programs.

Chris Hargarten, product manager for Visual C++, says the problem's been around since 1995, but it wasn't discovered until recently.

"Any time [the first day of] daylight-saving time falls on April 1, [the Library] won't calculate the time difference correctly for a week," Hargarten said.

Hargarten says Microsoft is aware of the problem and has been working on a solution for some time.

Software engineer Richard Smith discovered the bug while experimenting with time-and-date functions in a program he was writing, and his report spread over the Internet.

"I was using Windows as the standard of what would be correct, and I found that the results didn't check out," Smith said. "Later we found out that the bug was caused by one missing equals-sign in a formula."

Many Applications Affected

After Smith sent off bug reports to Microsoft and Netscape Communications, he researched the problem and discovered that on his hard drive alone "about a hundred applications" refer to the Library, requesting information contained in the file.

Applications that need date information can obtain it from two places: the operating system or the Library. The problem doesn't show up when a program asks the operating system for the date, but only a few applications do that.

Many developers prefer to use the Library (as Smith did) as a foundation to their own applications. Those who used any version from 4.1 onward will likely be affected by the problem. The Library is also a key component of the Windows 95, 98, and NT operating systems.

Smith has posted a simple Web page that helps people test their browsers for the problem (see link on right.)

"I can't think of one bug that's going to hit so many people at once," Smith said.

What's an Hour to You?

Some people may never even notice the bug. If it hits in the first week of April 2001, the worst that will happen will be that users in the U.S. and Canada will find that some applications report the time an hour later than it should be.

Microsoft's Hargarten downplayed the bug's significance. "There's been a lot of speculation, and I can't come up with a really harsh scenario where the bug will take effect," he said.

But the nuisance factor of this error could be high, says Smith. He suggests that Windows PC-based computerized wake-up calls in hotels could come late. Personal information manager software may report meetings at the wrong time. Bank ATMs, which rely on an accurate accounting of the time of each transaction, might have their dates "tainted" by Windows NT server software.

Smith calls the fix trivial, and Hargarten called the problem "a simple bug." But because the Library code is linked into so many applications, the scope of the problem is enormous.

Users will likely need to obtain update patches for their software (or newer versions), as well as a patch for their operating system. Microsoft plans to announce a release date for software patches within a week on its Support site.

--Andrew Brandt is an associate editor for PC World and writes the weekly Don't Bug Me column for PC World Plus. He can be reached at dontbugme@pcworld.com.

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