According to an article from the Lexington Herald-Leader that discusses work by Cliff Arnall of the University of Cardiff in Wales in which he determined that January 23rd was the worst day of the year. Especially poignant for those in Canada, where elections are held today.

BBC News ran an article about the happiest day of the year which also cited Mr. Arnall's work, but used a different formula that left out the financial component completely.

Interestingly, the happiness and sadness formulas are not the same. This makes some sense, though, if you look at the things that "drop out" of the equation for the happiest day.