What is a Millennial?

Wikapedia states "Millennials are the demographic cohort following Generation X. There are no precise dates when the generation starts and ends."

I was hoping there were some experts on this site that could help whittle through the definitions of a Millennial; I found the following:
? According to Iconoclast, a consumer research firm, the first Millennials were born in 1978.
? Newsweek magazine reported that the Millennial generation was born between 1977 and 1994.
? In separate articles, the New York Times pegged the Millennials at 1976-1990 and 1978-1998.
? A Time magazine article placed the Millennials at 1980-2000.
? Census has revealed that Americans born between 1982 and 2000
? Howe and Strauss define the Millennial cohort as consisting of individuals born between 1982 and 2004.

Any help would greatly be appreciated!  Thank you so much!