Given that January 1, 2004 was Thursday.

Odd days in 2004 = 2 [because 2004 is a leap year]

Also note that we have taken the complete year 2004 because we need to find out the odd days from 01-Jan-2004 to 31-Dec-2004,

that is the whole year 2004

Hence January 1, 2005 = Thursday + 2 odd days = Saturday