It is possible to find some clear understanding of Century Rollover issues looking at recent PC chip-sets specifications made by Intel .
Modern chip-sets like those of Intel 6 Series ( see specs ) sets a special bit when a transition from year 99 to 00 occurs. That generates an SMI ( a special code managed by Bios firmware ) when the machine is in S0 state.
S0 state means that machine is fully operational : in this case firmware code can react immediately and update the century byte ( Smi handler should be executed before any similar operation programmed by the running Operating system .I think that a possible conflict in this sense has to be fully verified by QA).
It could be that machine is in a different power state during transition from year 99 to year 00 :machine could be in standby or in power off or in hibernation .In this case firmware code should correct the Century byte as soon CPU will restart normal execution .
Using this approach based on Intel recomandations , transition to new century will proceed smootly and without specific issues in all power states.
Vincenzo Ianieri molise@molise.com