What age range is considered "middle-age"?

What age range is considered "over the hill"?
44 - 55

What age range is considered "senior"?
60+

Is "over the hill" and "senior" the same thing?
No

What are the age-based generation names (e.g., Generation X), and what years do they represent?

GenX, according to Douglas Copeland who wrote the novel Generation X, begins in 1962 (to '79).. I was born in late '62 and def not a Boomer. Sometimes '61 - '64 is called the "Jonesers" or the "lost generation."

2000 to present: Generation Z
1980 to 2000: Millennials or Generation Y
1962 to 1979: Generation X
1946 to 1961: Baby Boomers
1926 to 1945: Silent Generation
1900 to 1924: G.I. Generation

I've heard different answers to these questions, so I'm hoping that someone can answer them as accurately as possible.

I had no idea that when I turned 40 years old five years ago I was considered middle-aged. Now I'm curious about the different age groups and when I'll hit the "over-the-hill" mark.

I would call "middle aged" ages 42 to 65.