Concept:The day of the week is found by counting the total number of odd days (days beyond complete weeks) from a fixed reference. Each odd day shifts the weekday forward by one.
Explanation:First, calculate odd days up to 31 December 2011. The years 1600 and 400 have 0 odd days each. The remaining 11 years (2001 to 2011) contain 2 leap years (2004, 2008) and 9 ordinary years. Odd days =
2×2+9×1=13. So odd days up to 2011 = 13.
Next, count days from 1 January 2012 to 15 July 2012. 2012 is a leap year, so February has 29 days. Days: Jan 31, Feb 29, Mar 31, Apr 30, May 31, Jun 30, Jul 15. Total =
31+29+31+30+31+30+15=197 days. Odd days =
197÷7 gives remainder 1.
Total odd days =
13+1=14. Final odd days =
14mod7=0. Mapping: 0 odd days corresponds to Sunday.
Answer:The day on 15 July 2012 was Sunday. Hence, the correct option is B. Sunday.