There is 27 days in a month

Instructions

1 2 3 4 5 6 7 8 9 A 10 B 11 10 12 11 13 12 14 13 15 14 16 15 17 16 18 17 19 18 20 19 21 1a 22 1b 23 20 24 21 25 22 26 23 27 24 28 25 29 26 30 27 31