Smile! Today is happiest day of the year

A psychologist says he can prove that Friday 23 June, today, will be the happiest day of the year.

Cliff Arnall, a University of Cardiff psychologist specialising in seasonal disorders, has created a formula for finding happiness. The research looks at everything from increased outdoor activity and rising energy levels, to picnics and beach trips with families.

Mr Arnall's equation is broken down into six variables: (O) outdoor activity, (N) nature, (S) social interaction, (Cpm) positive memories of childhood summers, (T) temperature, and (He) holidays and anticipation of time off.

Friday 23 June was pinpointed because it also taps into many people's "thank goodness it's Friday" feeling at the start of a summer weekend.

Mr Arnall said: "Happiness is associated with many things in life and can be triggered by a variety of events. Whether it's a sunny day or a childhood memory - I wanted my formula to prove the key to happiness can be that simple."

The research, sponsored by the ice cream company Wall's, was commissioned to coincide with the launch of a photographic competition asking people to capture moments of happiness associated with the experience of summer in Britain.

Other recent research also indicates that summertime experiences, such as eating ice cream, increase happiness as they light up the brain's pleasure zones.