| Microsoft Year 2000 Readiness Disclosure
& Resource Center |
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| Windows Operating System Interactions
with BIOS and Real Time Clock |
| 5. Common
Rollover Errors
Three
common RTC/BIOS error cases and how date errors would be passed on
to the operating system: Case 1
The century rollover code is missing from the BIOS program and
the RTC century register is not updated.
During POST, the BIOS may not map invalid dates like 1900 to
2000. For example, if the PC was turned off during the transition
from the year 1999 to 2000, the century register will still be set
to "19" (1900) when the machine is turned on. Case 2
The BIOS only allows years within a specific range.
During POST, the BIOS may not allow certain valid date ranges.
For example, one commonly-used BIOS chip allows the years 1994 û
1999 and 2094 û 2099, but does not allow the years 1980 û 1993 or
2000 û 2093. Case 3
BIOS Setup does not recognize dates after December 31, 1999.
When running BIOS Setup, a date of 1/1/2000 or greater may not be
accepted.
General Note Some software development applications use a
file-based version control system that affixes a "time stamp" to
data files. This time stamp contains date information obtained from
the system clock. If the BIOS/RTC fails to reset the system clock to
January 1, 2000 (and if the operating system does not automatically
correct the date) new files and new versions will be saved with
incorrect time stamps. This could affect data in the history
database. For example, if the version control system checks in a new
version with an incorrect time stamp (say, a date in the 1900s), the
control system could overwrite the 'new' version with an older
version of the data file. For more information on how Microsoft
application development tools are affected by BIOS/RTC errors, see
the Year 2000
Product Guide.
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