Should you keep quiet about your age, or wear it with pride? The importance we attach to age is relatively recent.

Age can be measured in more ways than one, say both sociologists and biologists. There is of course chronological age, but there is also cellular and social aging. The search for new definitions of old — and young!

Source: Age May Be Just A Number, But Which One?

It’s interesting to note that the threshold for old has changed dramatically over time. In the 17th and 18th centuries, at least in the West, 40 was the magic number. In the 19th century, that limit was pushed to 50. Nowadays, several studies show that people consider old age to begin at 69, on average. People under 25 believe it begins at 61, while those over 65 say it’s 77. And 8% of people say old begins at 80.