Thirty-seven is the age by which most men are settled in a happy relationship and have formed a close circle of friends with which to socialise, according to a study by a UK menswear brand.
The dreaded 'mid-life crisis' is still a decade away and their troubled angst-ridden teens are a fading memory, the Daily Mail reported.
Becoming a father is a particularly rewarding experience with a beaming 43 per cent of men say becoming a parent was one of the happiest days of their life, the study by Jacamo found.
It was followed by getting married, with 35 per cent rating it as one of their top three happiest moments in life, and seeing their favourite football team win the league (18 per cent).
Other memorable happy moments include buying a house (17 per cent) or car (7 per cent), proposing to a partner (13 per cent), and graduating from university (9 per cent).
Experts say these are all milestones many men are likely to have passed by the age of 37 and could explain why it is the 'age of happiness'.
Phillip Hodson, fellow of the British Association for Counselling and Psychotherapy, said men of 37 typically benefit from health and life experience.
"It would be logical to think that men would be happier when they are younger, when they are fitter and healthier. As men get older they become more prone to illness and more feeble," he said.
"At 37, you are young enough not to be disillusioned by life, which comes with the midlife crisis. But you are also old enough to have developed self-confidence, earned some respect and authority and to have a sense of achievement," he added.
Day to day, eating a favourite lunch is the one activity most likely to put a smile on a man's face, the poll of 1,000 men revealed.
Splashing out on DVDs, clothes and gadget makes a gloomy day shine for 28 per cent of men, and hanging out with friends is a boost for 27 per cent.
A quarter, 26 per cent, enjoy an innocent flirt, 22 per a decent cup of tea or coffee and 20 per cent a surprise dinner cooked by the woman in their life.
Others are happy when they find time to read the news (11 per cent), achieve a new top score on a computer game (8 per cent) or simply receive a text message (5 per cent).
Romantic men are happiest when spending time with their partner, followed by their mates and children.
However, just 5 per cent are happy when in the presence of workmates.