Feeling more happy than usual this particular Friday? You should be, according to a scholar in seasonal disorders at a British university.

Cliff Arnall of Cardiff University has analysed such factors as outdoor activities, nature, social interaction, childhood memories, temperature and holidays -- data gathered over a period of 15 years in interviews with 3,000 people around the world.

His conclusion: June 23 is the happiest day of the year.

"People across borders experience happiness when they meet with friends and family and establish close social relationships," the University of Cardiff academic said. "We need some close emotional ties."

He used what he considers a "simple equation" to reach his conclusion -- O + (N x S) + Cpm/T + He.

O stands for outdoor activities, 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.

Arnall has already figured out the saddest day of the year. It was January 23 -- a Monday. "Surprise, surprise", he quipped.