IBM Year 2000

PC Year 2000 The Hardware Clock is Ticking
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Clock

IBM has dramatically improved function and performance of IBM PCs since the first product was introduced in 1981. While IBM PCs have always been capable of correctly processing date information as data, newer IBM PC models are better able to update their internal clock for the millennium change.

How your Computer keeps time
All IBM machines since the AT model contain a digital clock in the hardware. The clock battery maintains the date even when the machine is powered "off". Operating systems (such as Microsoft Windows 95 and NT) rely on the PC hardware clock to set their own date and time services each time the system is started up.

The hardware clock automatically updates the last two digits (1998) of the date with each passing year. Consistent with PC industry standards, however, the task of updating the first two digits (1998), called the century digits, is left to the system BIOS (Basic Input/Output System).

Legacy IBM PCs
For most IBM PC models introduced before 1996, the BIOS did not include the ability to update the century digits of the hardware clock for the millennium change. Therefore, the hardware clock's century digits may be incorrect after the Year 2000 occurs (e.g., 1900 instead of 2000). When these PC models are later restarted, the operating system may set its own date incorrectly. As a result, software programs may make mistakes when performing date-dependent tasks.

Some current operating systems may try to directly update the hardware clock's century digits for the millennium change. If you desire specific information about your operating system, you should contact the operating system developer directly.

We recommend that users take the simple step of resetting the system date on their older (AT and later) IBM PC on or after January 1, 2000. This will reset the hardware clock for the new century. Strategies to Meet the 2000 Challenge can guide you through these steps. Once reset, the hardware clock is capable of keeping the correct date when restarted.

For some older models, BIOS updates are available, which improve the PC's ability to update the century digits of the hardware clock.

Year 2000 Ready IBM PCs
For most new IBM PC models introduced since 1996, the BIOS can automatically update the century digits of the hardware clock correctly when the system is restarted after the Year 2000 occurs. All current IBM PC models have this capability. IBM designates these models as "Year 2000 Ready".

On many Year 2000 Ready PC models, the BIOS can automatically update the century digits of the hardware clock correctly if the machine is powered "on" during the century transition. Some operating systems, however, de-activate the BIOS timer service after starting the system , preventing this automatic BIOS function from working.

Even if the BIOS is not able to immediately update the hardware clock while powered "on" during the millennium transition, software programs available on the market today should not be affected if they are Year 2000 ready and follow good programming practices. Year 2000 ready operating systems are expected to keep and update the date correctly after startup using their own services. Year 2000 Ready application programs are expected to obtain date information from the operating system or BIOS service routines, not from the hardware clock directly. If a program does take date information directly from the hardware clock, it might make mistakes when performing date-dependent tasks. If you desire specific information about your operating system or application programs, contact the software developer directly.

We recommend that users take a simple step on or after January 1, 2000 to enable their Year 2000 ready IBM PC's hardware clock to reset for the new century. Just turn the system off and then back on again, or restart the operating system.

Strategies to help you meet the Year 2000 Challenge