What's the cutoff between the millennial generation and whatever is the one to come after it? 2000?
To me the two defining characteristics for the millennial generation have been the spread of the internet in the mid 90s and the experience of 9/11 in 2001. If you neither of those things occurred while you were a kid/teen (7-17) then you aren't a millennial. So I would say the millennial generation roughly covers the birth years of 1978-1994. I think people born in the mid 80s are the "truest" millennials because we experienced both of the above events while we were in the 7-17 age range.
The upswing in births is a better marker for the start, and that would be in 1982-83. Very few sociologists would end it as soon as 1994. Some have suggested that the end point can't yet be determined since one needs data on the young adult population to make that call.