Two enums have some elements in common, why does this produce an error?

Question

I have two enums in my code:

enum Month {January, February, March, April, May, June, July,
        August, September, October, November, December};
enum Shor         


        

Answer 1

typedef enum {Jan, January, Feb, February, Mar, March, Apr, April, May, Jun, June, Jul, July,
    Aug, August, Sep, September, Oct, October, Nov, November, Dec, December} Month,ShortMonth;

Merge them become one