O + (N xS) + Cpm/T + He

Psychologist Cliff Arnall arrived at this formula for predicting happiness in an effort to "get people talking about what makes them happy."

O = Being Outdoors
N =  Connecting with Nature
S = Social interaction
Cpm = Childhood positive memories
T = Temperature
He = Holiday expected (vacations in America)

According to his calculations, June 20 is the happiest day of 2008. He notes that "the feeling of optimism caused by the combination of lighter evenings, the prospect of holidays and memories of childhood summers" tend to be highest each year around the summer solstice.

This is only a measure of external factors, however. To approximate how much subjective satisfaction one is able to derive from ideal conditions, consider this formula from Shinzen Young:

Satisfaction = Pleasure ÷ Grasping

He observes that a person’s subjective sense of satisfaction is inversely proportional to the degree to which the pleasure is subject to grasping. Conversely, a person’s subjective sense of satisfaction is directly proportional to the intensity of pleasure present and the degree to which one can monitor that pleasure with specificity.

In other words:

• When grasping goes up, satisfaction tends to decrease.
• When mindfulness goes up, satisfaction tends to increase.