The Baby Bust. In 1965 the birth rates collapsed which is where the Xers start and which is why Gen-X is often referred to as the Baby Busters
The Birth rates picked up again in 1976 so it's often used as the start of Gen-Y or the Echo Boom. Though often 1982 is the start because the milestone year 2000 would have been the year they graduated High school hence their name Millennials.
I was born in 1977, my brother in 1981. Vehicles such as the Honda Element or the Toyota Scion appeal to neither of us so I don't think we're Gen-Y, but rather, Gen-X. At least, that's how I figured it out. All of the cars that are marketed to Gen-Yers I find to be horrendously ugly.
Thanks for the ping!