IP: more on April 1, 2001 bug in Windows -- for real from our own John Markoff

[Dave Farber <farber () cis upenn edu>]

> New York Times News Service via Dow Jones
> By JOHN MARKOFF c.1999 N.Y. Times News Service
> As if all the panic over the infamous Year 2000 computer glitch were not
> enough of a problem, experts now reveal that the omission of a single equal
> sign has created a time-related error in Microsoft Corp.'s Windows family of
> operating systems that will next appear on April 1, 2001.
> The timing, it turns out, has nothing to do with April fools jokes but rather
> with an error in calculating the beginning of daylight savings time. The bug
> causes Windows applications to behave as if it is one hour earlier than the
> correct time shown on the Windows clock. The problem will continue for one
> week, until April 8, 2001, when the applications will shift to daylight time
> and again be in synch with the operating system and the rest of the nation.
> The bug, which affects programs running under Windows 95, 98 and NT, was
> discovered by a Massachusetts programmer and was confirmed by Microsoft
> Monday.
> While not as threatening as the Year 2000 problem, the flaw could prove
> significant for programs that require precise time information.
> One possible widespread nuisance, for example, could be inaccurate alarms
> from thousands of hotel wake-up systems that automatically ring the phones of
> sleeping guests.
> ``What happens in a hotel when 50 people don't get their wakeup call on
> time?'' said Richard Smith, president of Phar Lap Software and the programmer
> who discovered the error and published it in an industry list of software
> bugs last week. ``Multiply this by 10,000 hotels and you're going to have a
> lot of angry people.''
> The defect is in a ``dynamic link library,'' a kind of file that ends with a
> period followed by the letters ``DLL.'' The way Windows is structured, such
> libraries contain instructions and data that are shared by any number of
> different programs written to run on the Windows system.
> The program will not have a significant impact on most home users, Smith
> predicted, but he said that ``financial institutions like banks, stock
> brokers and e-commerce sites are going to care a lot about this bug; they
> need accurate records of all transactions for accounting purposes.''
> ``This will be a major headache and expense,'' he said.
> Although the bug's ultimate impact is difficult to determine, Smith estimated
> that as many as 40 to 50 million computers could be affected.
> The flaw, Smith said, results from the fact that April 1, 2001, falls on a
> Sunday, which confused a small algorithm in the library file that checks for
> the start of daylight time.
>
>
> (a classic fence post bug, i'm told)
> -------
>
> The library, he said, contains a less-than symbol where it should have a
> less-than-or-equal symbol. This causes a one-week delay in invoking the start
> of daylight time.
>
> -------
>
>
> Smith said that preliminary checks of other operating systems indicated that
> the bug did not appear in Sun Microsystems Inc.'s Solaris and that it
> appeared to have been corrected in a test version of Windows 2000. He had no
> data on Apple's Mac OS.
> In most cases, it will be possible to fix the problem by simply obtaining a
> new version of the flawed library, he said. However, in some cases, certain
> programs will not be corrected by simply replacing the flawed library,
> MSVCRT.DLL. Certain applications that depend on that library might need to be
> fixed independently by the original software developer, Smith said.