If 18 october 2006 was Wednesday, then what was the day of the week on 17 October 2000?

If the number of days between two dates is multiple of 7, they will have same day.

Let us assume the day on 17 Oct 2000 be X

Number of odd days from 17 Oct 2000 to 31st Dec 2000 = (14+30+31)/7 = 75/7 = 5 days

Number of odd days in 2001, 2002, 2003, 2004, 2005 will be 1, 1, 1, 2, 1 days respectively (2004 is leap year) = 1+1+1+2+1 = 6 days

The number of odd days from 1st Jan 2006 to 18 Oct 2006 is = 3+0+3+2+3+2+3+3+2+18 = 39 days

Therefore, total odd days = 5+6+39 = 50/7 = 1 days

If the day on 17 Oct 2000 be X then on 18 Oct 2006 day will X+1

Thus, 17th Oct 2000, day will be Tuesday.