There are 31 days in january.
There are 30 days in september.
There are 31 days in december.
may found at index 8
Alphabetical listing:
april has 30 days.
august has 31 days.
december has 31 days.
february has 28 days.
january has 31 days.
july has 31 days.
june has 30 days.
march has 31 days.
may has 31 days.
november has 30 days.
october has 31 days.
september has 30 days.
After erasing may:
april august december february january july june march november october september 
After erasing months 2, 3, 4, and the last one:
april january july june march may november october 
After inserting frobuary,42:
april august december february frobuary january july june march may november october september