Ananova:

An academic has worked out a mathematical formula which he says proves June 20 is the happiest day of the year.

It is down to a combination of lighter evenings, the prospect of holidays and memories of childhood summers, reports the Daily Telegraph.

Cliff Arnall, a psychologist and former tutor at Cardiff University, worked out the equation: "O + (N xS) + Cpm/T + He".

O stands for being outdoors, N is nature, S is socialising with neighbours and friends, Cpm stands for childhood positive memories, T is the mean temperature, and He is holiday expectation.

However, his formula fails to take into account falling house prices, rising inflation, stagnating pay rises or the fact that none of the home nations are in Euro 2008.