Why not do this all the correct way - with a data array?
Create a structure for all your desired data, such as:
struct YearParts {
int monNum;
int monSize;
string monShort;
string monLong;
bool leapYr;
};
Assign them to an array - you may even make the array length 13, and make your Jan as index 1.
You could, if you wish, still use your enum as an alternative way to select an index.
They could be made public, put in an include file, and be available everywhere as your personal standard.