Today, Friday, June 23, is the happiest day of 2006.

We have it on the authority of no less than Cliff Arnall, the psychologist in Wales who calculated that Jan. 23 was the most depressing day of the year. You may recall the day. It was election day in Canada.

Arnall's work is not rocket science, or even very serious science, but it gets him into the headlines.

His happiest-day pronouncements are sponsored by an ice-cream company, a fact that ties in nicely with his view that fond memories of childhood summers are a key to human happiness.

But he doesn't just look at the calendar and pick a likely date (the first Friday of summer, for instance). He uses a scientific formula: O + (N x S) + Cpm/T + He.

As he explains it, O stands for being outdoors and outdoor activity, N for nature, S for social interaction, Cpm for childhood summers and positive memories, T for temperature and He for holidays and looking forward to time off.

When he crunched the numbers in 2005, the happiest day turned out to be the first Friday of summer. In 2006, same story.

Arnall's academic affiliation is with Cardiff University, where he is a part-time teacher in the extension department. On the side, he offers "practical and entertaining training seminars and lectures" on such topics as "sleeping, dreaming, napping and dealing with tiredness."

"Happiness," he told the BBC in 2005, "is associated with many things in life and can be triggered by a variety of events.

"Whether it's a sunny day, a childhood memory, or something as effortless as eating a delicious ice cream, I wanted my formula to prove the key to happiness can really be that simple."