I think the terms are defined this way:
Millennials, born between 1980 — 2000
Generation X, born between 1960 — 1980
Baby boomers, born between 1946 — 1965 (overlap with Gen X)
Silent generation, born during the Great Depression and World War II
There will soon be a new one, the oldest post-millennials are 14.
…unlike the generations just before them, Millennials seem to be avoiding marriage, church and political affiliation, and to lack a sense of social trust. Only 19 percent say that generally speaking most people can be trusted, compared to 31 percent to 40 percent among older generations.
This is in line with Harvard political scientist Robert Putnam’s thesis that social trust is declining in America. The Pew analysts speculate that this may result, as Putnam has uncomfortably concluded, from increasing racial diversity.