Validation of user input ( month/day)

[EmilKh]

User has to input date in mm/dd format, anything else creates error:

cout << "Please enter the month and day (mm/dd) >> ";
cin.getline(buffer, 80);
		
if (strpbrk("/", buffer))
{
	month = atoi ( strtok(buffer, "/") );
	if (NULL)
		day = atoi (strtok(NULL, "\n") );		
}
		
if (month < 1 || month > 12 || day < 1 || day > 31)
	cout << buffer << " is not a valid date.";

It's working in 99.99% cases. 0.01% is input like "/", which screws me up and "Bus error" appears. Any ideas?