What day of the week was 31 January 2007?

Wednesday

Using Code Method :-

\(\frac{Date+Month code+Year code+Last 2 digits of yr+Leap yrs till given yr}{7}\)

( Note: Remainder of the above sum will be the code of week day }

31 Jan 2007;

31 + 01 + 06 + 07 + 01 = 46

remainder of \(\frac{46}{7}\) = 04

Therefore, the code of 04 is Wednesday