Just been to a conference and listened to a talk on this subject.
Apparently there is a fair bit of difference between the ages considered correct for each generation. Generation Y is also known as Echo Boomers. The literature all makes up its own definition of each generation and there are hardly any (I believe the professor said he found 2) studies showing statistical significance between generational differences, in their hopes, dreams, fears, careers, family etc. His own research on careers with 1000 respondents, found no statistical significance - hence no journal is interested in publishing it. The generational differences therefore appears to be a great myth. He suggested that this myth is generated by HR people who earn millions teaching managers how to handle gen Y and people who earn millions writing books about the differences - talk shows also getting mileage out of it.
There are differences ofcourse between 20 year olds in the work place and 45 year olds - but of course - it’s just not related to which age you were born in, it is to do with maturty and experience.
Also, interestingly enough, many baby boomers are finding that they relate to gen Y - feeling lost sense of direction, needing to get fulfilment out of their work etc.