Date/time defauting to Dec 2000. Whenever I log on after the computer has been turned off, the

Question

Whenever I log on after the computer has been turned off, the date defaults to December 2000. It appears to be a millenium issue.I have tried the setting to ON for "Automatically synchronize with an internet time server" and also tried with that unchecked..........neither solves the problem. The machine seems to run slower until I correct the time/date to current. What should I try?