The year next to 1991 that will have the same calendar as 1991 is

The 1991 calendar repeats when the odd days counted from 1991 total a multiple of 7.

1991 is an ordinary year that begins on Tuesday.

Ordinary years give 1 odd day and leap years 2, so add them year by year from 1991.

1 + 2 + 1 + 1 + 1 + 2 + 1 + 1 + 1 + 2 + 1 = 14 by the end of 2001.

14 is a multiple of 7, so the matching calendar year is 2002.