enum 2 int back 2 enum

Hi Experts,

I have an enum type declared like this:

enum _en_Monts
{
   January = 1,
   February,
   March,
   April,
   May,
   June,
   July,
   August,
   September,
   October,
   November,
   December
};

Then I have this piece of code:

_en_Monts aMonth = June, anotherMonth = August;

long ulMonth = aMonth;

anotherMonth = *(reinterpret_cast<_en_Monts *>(&ulMonth));

MSDN claims that the last sentence is correct but the result is undefined. Is this the real case?

PS: Here is the example from MSDN

// Example of the enum keyword
enum Days               // Declare enum type Days
{
   saturday,            // saturday = 0 by default
   sunday = 0,          // sunday = 0 as well
   monday,              // monday = 1
   tuesday,             // tuesday = 2
   wednesday,           // etc.
   thursday,
   friday
} today;                // Variable today has type Days

int  tuesday;           // Error, redefinition of tuesday

enum Days yesterday;    // Legal in C and C++
Days tomorrow;          // Legal in C++ only

yesterday = monday;

int i = tuesday;        // Legal; i = 2
yesterday = 0;          // Error; no conversion
yesterday = (Days)0;    // Legal, but results undefined

// end of sample

This last line intrigues me. I run my code and it worked, but can I be sure that it always will?

Thanks.