If it was Sunday on 5th April 1998, then what was the day of the week on 5th January 2005?

There are two leap years between 5 th April 1998 and 5 th January 2005 i.e., 2000 and 2004. As, number of odd days in a normal year is '1' and number of odd days in a leap year is '2'. So, number of odd days from 5 th April 1998 to 5 th April 2004 is: (1 + 2 + 1 + 1 + 1 + 2) = 8 As, the number of odd days in a month, which has 30 days is '2' and the number of odd days in a month, which has 31 days is '3'. So, the number of odd days from 5 th April 2004 to 5 th January 2005 is: (25 + 3 + 2 + 3 + 3 + 2 + 3 + 2 + 3 + 5) = 51 Therefore, total number of odd days is (8 + 51) = 59 The days of the week repeat itself after 7 days. Thus, the number of odd days = 3 As, on 5 th April 1998, it was Sunday, so, on 5 th January 2005, it will be Wednesday.