Boomers, Millennials, Gen X/Y/Z - generations explained

I get very confused when I read about Millennials, Generation X, Generation Z, etc, etc. So, here are all those generations and demographic cohorts in black and white:

• Baby Boomers (also known as the Me Generation) refers to the generation born after the Second World War, usually meaning from 1946 to about 1964.
• Generation X (or just Gen X) are those born anytime between the early 1960s and the early 1980s.
• Generation Y (also known as Millennials, Generation We, the Global Generation, Generation Net, etc) are those born just before the millennium, usually taken to mean anywhere from about 1980 to 2000.
• Generation Z is the latest cohort, and refers to those born after the late 1990s or early 2000s.

Now, these dates are not fixed or definitive, and, as can be seen, there is also some level of overlap. But at least I can refer to this page to try and keep things straight in my ageing Boomer head.

UPDATE
For what it's worth, the influential Pew Research Center has recently tried to refine these definitions:

• Silent Generation: born between 1928 and 1945 (currently 73 - 90 years old).
• Baby Boomers: born between 1946 and 1964 (currently 54 - 72 years old).
• Generation X: born between 1965 and 1980 (currently 38 - 53 years old).
• Millennials: born between 1981 and 1996 (currently 22 - 37 years old).
• Post-Millennials: born after 1996 (currently 21 or younger).

One question occurs to me: why would the Pew Research Center - a respected American think-tank and polling organization - even bother?