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Millennium problem

Posted on 1998-10-10
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Last Modified: 2010-04-26
L.S,

What is a good way to check whether my computer is millennium-proof or not?
Regarding DOS, CMOS and Windows 95 OSR 2.

Thanks for a reply!

A. Tanis
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dunnaway earned 100 total points
ID: 1011303
Found this at http://www.adppro.com/cmosy2k.htm

The Standard PC maintains two system dates; one is in the CMOS Real Time Clock (RTC) chip - a hardware component that is normally on the machine's motherboard; and the other one is in the DOS (and Windows) operating system software. These two dates are represented differently. The CMOS RTC date is kept as century/two-digit-year/month/day and the DOS date is kept as days since 1980/01/01 which is convered to four-digit year/month/day when called by any program.When DOS boots, it normally initializes its current date by reading the date in the CMOS RTC and converting it to days-since-1980/01/01. DOS maintains its date as long as the system is running; the CMOS RTC hardware maintains its date whether the system is runing or not (that's one of the reasons for the little battery on the motherboard), but it does not
maintain the century. In the CMOS RTC, year 99 overflows into 00 and the century remains unchanged so the effective year becomes 1900; in DOS year 1999 overflows to 2000. So, until the system is rebooted, there will appear to be no problem with the transition from year 1999 to 2000; but trouble lurks in the the CMOS RTC, which has become year, you guessed it, 1900. When DOS boots, it reads 1900 as an out-of-range date from the CMOS RTC and the date conversion algorithm calculates an erroneous
1980-01-04. That is what the DOS date will become after rebooting the system after the year 2000 transition if the CMOS RTC exhibits the flaw.

Now for the test: To determine if your system suffers the year 2000 CMOS RTC flaw, from a DOS prompt:

         Power off test:
         set the date and time to

              C:>DATE 12-31-1999

              C:>TIME 23:59

         Power off the system, wait for more than one minute.

         Power on the system. Allow system to boot.

         Check the DOS date:

             It should read 01-01-2000. If it reads 01-04-1980 your machine has the flaw.

         Power on test:

         set the date and time to

              C:>DATE 12-31-99

              C:>TIME 23:59

         Wait for more than one minute.

         Check that the DOS year has changed to 2000.

         Reboot. The DOS year should still be 2000, if not, your machine has the flaw.


Hope this helps
dunnaway
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