RTC day of week

[xenos]

Many CMOS maps say that 06h contains day of week, valued from 1 to 7 where 1 means sunday. However, _my_ computer does not work this way and even bochs does something different. Has anyone else encountered this problem, or even solved it?

[Stefan]

It is true, CMOS 06h contains the day of week, but since the weekday is updated independently of the time, it is bound to be inaccurate. Any other value in the register (besides 1-7) tells the RTC "don't keep track of the day of week". On most computers, CMOS 06h is set to 0. It would definitly be wise to compute the weekday yourself... I seem to recall John Horton Conway (of Game of Life fame) created a good weekday algorithim, (begin (google-search "Conway" "Doomsday Algorithm") (exit 0)).
Just curious: Why did Intel/IBM of all people use a Motorola RTC chip on their PC/AT+ motherboards?