In which year will the calendar of 2100 be repeated for the first time?

Explanation

1. 01

   2100 is a century year not divisible by 400, so it is an ORDINARY year, beginning on a Friday.

2. 02

   Look for the next ordinary year beginning on Friday. Odd days: 2100 (1), 2101 (1), 2102 (1), 2103 (1), 2104 leap (2), 2105 (1). Total $= 7$.

3. 03

   So 1 January 2106 is a Friday, and 2106 is ordinary: the calendar repeats in 2106.