Is there a way to fix my enumerated value getting the ambiguous error?

Question

I have an enum months:

enum months{jan = 1, feb, mar, apr, may, jun, jul, aug, sep, oct, nov, dec};

However, when I am trying to use these enum values in an array:

int months[12] = { jan, feb, mar, apr, may, jun, jul, aug, sep, oct, nov, dec };

The problem I am having, is in the Error list I am getting:

'oct' is ambiguous
'dec' is ambiguous

My guess as to why this is happening is that it is something to do with the words oct and dec, because when I change the words it gets rid of the error.

Does anyone know a fix for this problem?

I'm also slightly curious as to the reason why this is happening.