Dates I have encountered (all disputed):
Boom 1946 - 1964
Gen X 1965 - 1976
Gen Y 1977 - 1995
If you do a web search, however, you can find references to Gen X beginning as early as 1961 and ending as soon as 1975 or as late as 1981. Gen Y, following the amorphous Gen X, has even less stable dates.
As the phenomenon of naming the generations was coined, it was a specific reference to a particular event with serious ramifications for the infrastructure of the country. The Baby Boom was a real phenomenon–a population explosion not offset by war or disease–that seriously taxed the resources of school systems, housing, and all the other aspects of planning that go into creating places where people may live.
Once people began talking about the Baby Boomers as if they were more than simply a bubble on the population chart, we started getting silly creating “identities” for “generations” (whom we then had to name so that we could know about whom we were inventing beliefs).
Take the Boomers, themselves. At different times they have been “idealists” and other times “cynics.” Sometimes Boomers are identified with yuppies, yet when yuppie was coined and came into broad circulation, the people described were actually younger than Boomers. Boomers, of course, were unpatriotic and refused to “defend their country” from the assaults of North Vietnam–which is why the majority of the names on the wall in Washington are of Boomers.
The idea that someone born in 1948 automatically shares some serious outlook and system of values with someone who was born in 1962 is preposterous. The person born in '62 was only eleven years old when the US. involvement in Vietnam ended, while the person born in '48 was pretty much compelled to take sides on the issue of U.S. involvement. The person born in '48 grew up “knowing” that the U.S. was the greatest country in the history of the world, only to watch the assassination of President Kennedy, race riots, the police riot at the Chicago convention, Kent State, war protests, and Watergate change their world while the person born in '62 saw those as merely historical events. (Television, the space race, steel-belted radial tires, banking more than 25 miles from one’s home, and a host of other changes also would have changed from “current events” to “history” within that generation.)
And the different ways these events might shape world views are ascribed to only one of the generations mentioned in this thread.
I am not claiming that different “generations” are not shaped by their times; only noting that the arbitrary boxes into which we are shoehorning people according to invented generational boundaries are misleading.