expressed by 16 (1980+16=1986). This technique optimized scarce system resources and also made file date comparisons much easier to implement.The inability of MS-DOS to recognize dates prior to 1-1-1980 may produce unusual behavior at the century rollover. The most likely scenario involves a system powered off at the time of the century rollover. For instance, on December 23, 1999, a user powers off his system and leaves for vacation. The user returns on January 3, 2000 and powers on the system. The RTC passes the date 1-3-1900 to OS. Since the earliest date MS-DOS recognizes is 1-1-1980, it interprets 1900 as invalid, and sets the date to its earliest known date, 1-1-1980 (or, in some cases to 1-4-1980). Further, if the PC is networked and the date on the server is likewise incorrect, the local system date will remain out of date.Possible SolutionsDells operating systems have integral date correction logic that can detect and correct an invalid date at the century roll over. They restrict access to the Real Time Clock or BIOS, so only those application programs can retrieve date information from the operating system. Dell has concluded that the operating systems and software applications obtain information primarily through the BIOS, therefore Dells solution should be implemented primarily in the BIOS. Most major computer manufacturers in the industry support this approach. Dell also concluded that the solution should not significantly impact system cost or reliability.An obvious solution would be to replace the Real Time Clock. This solution recently became available during the beginning of 1998 when date century compliant Real Time Clocks were available in commercial quantities. Regrettably this brings upon significant drawbacks. First of all, it is not practical or economically feasible to upgrade. Secondly by adding a new Real Time Clock chip will only impact the cost, reliability, and performance of the PC system. F...
