According to this Daily Mail article, it is 23 and 69:
From sweet 16, to the milestone 21st birthday, to life supposedly beginning at 40, there are all sorts of theories about the age that signifies you’re in you’re prime.
But now researchers have pinpointed the two ages in adult life when you’re likely to be at your happiest – and they might well surprise you.
According to experts from the London School of Economics and Political Sciences, happiness peaks at the ages of 23 and 69, My Domaine reported.
To draw this conclusion, researchers questioned 23,000 volunteers, aged 17 to 85, and found that happiness goes in a U-shape, bottoming out in middle age and peaking again at the other end of the spectrum.
Typically, 23 is an age when many people have finished third level education and are looking forward to starting their careers and earning a real income for the first time, with all the freedoms that brings.
At the age of 69, a lot of people will be ready to enjoy retirement and have the stresses of raising a family behind them.
Notice that the theme here seems to be that people are happiest when not raising a family. Everyone in-between is probably dealing with a lot more stress.
At 23, I still had years of grad school to go for a PhD, so I can’t say that was my happiest and I am not 69, so don’t have a comparison as of yet. I felt very happy in my early to mid-thirties when my health was better, which leads me to think that happiness is an individual situation for the most part.
How about readers, what were your happiest years?