Generate response to the question/instruction based on a piece of given material

Question/Instruction: Summarize the main points of the article about how different generations perceive old age and youth.

Given material: Yes, our perception of old is a moving target, and it depends on … well, it depends on how many candles you’ve managed to collect on the birthday cake.
If you want proof that old age has become a flexible milestone, look no further than the 2017 U.S. Trust Insights on Wealth and Worth report that shows how four different generations view senior citizenship. Not surprisingly, the older you are, the longer it takes to achieve such status.
For the silent generation, those 73 or older, senior citizenship arrives at 73, the exact same age baby boomers also selected as the beginning of twilight. Millennials, the generation between 21 and 36 years old, clocked it at 59 and Generation X, the 37- to 52-year-olds, at 65. For me this is proof that old age, like beauty, is in the eye of the beholder.
The generations were similarly divided when it comes to pinpointing the end of youth. The silent generation puts it at 35 and boomers and Gen Xers at 31. Millennials, however, believe one stops being young at 40. Which may explain why this generation, often criticized (wrongly, I believe) for taking too long to grow up, has popularized the term “adulting,” the long and overwrought process of accomplishing certain markers (i.e., getting a job, moving out of your parents’ home, marriage and children) on the way to independence.
Sorting through old black-and-white photos I inherited from my mother, I found one of my paternal great-grandmother, a formidable woman whose limited education did little to dampen the fierce ambition she had for her children and grandchildren. In the photo she wears a black dress notable for its absolute lack of shape and charm. Gray hair bound in a net, she scowls at the camera.
I gauged her age at 80. But judging from the setting and the other people in the picture, my father said she was, more likely, in her early 60s. How then did she look so ancient? Then I remembered the advice my father gave me a few months ago, when I turned 60: “From now on every day is a gift. In your grandmother’s time, many didn’t even make it to this birthday.” It was an unusual comment from a person whose family is known for its longevity.
If 60 was accepted as old at the beginning of the 20th century, when babies born in 1900 had a life expectancy of 50, it certainly isn’t considered so anymore. Modern medicine has extended our life spans and we, in turn, have stretched the passages that mark the road from spring to winter.
Today, age truly is just a number. “Old” is no longer a facile label. While there’s no denying the inexorable march of time (dimming eyes and creaky joints being my least favorite), attitude may prove to be the elusive Fountain of Youth. A zest for life, an interest in the world, the pursuit of a passion, a desire to learn, a conscientious effort to keep mentally and physically healthy — those seem to be more telling qualities of true youth.
On those terms, I plan to remain a perpetual 32.
This prompt doesn't seem malicious.