About RTC Date Roll Over

[FlyingDancer]

I have read some articles, knowing some infomation such as 1.Setting the time to 23:59:59 on the 29th or 30th day of a month that has less than 31 days may cause the clock to roll over incorrectly with some chipsets(What is the reason?) 2.y2k problem and so on Can you tell me 1.whether there exist some other situations like these problems, and what are they? 2.Should I access to the cmos RTC date or the OS date to test the date's validation? 3.How to chang and update the CMOS RTC time/ System Time