The 11 years in question must comprise a whole number of weeks. Suppose n of those 11 years were leap years. Then 365 * 11 + n is divisible by 7. Since leap years occur every four years, n is certainly less than 7. From here, n = 3.

Indeed, January 1st fell on a Monday on 1990, 1996, 2001 and 2007. Between 1990 and 2001, the following were leap years: 1992, 1996 and 2000. Between 1996 and 2007, the following were leap years: 1996, 2000 and 2004.