The Formula
Blue Monday was first identified by Cliff Arnall, formerly of Cardiff University, marking the symbolic time in January when people suffer from a series of combined depressive effects.
Blue Monday was devised using the following mathematical formula:

The model was broken down using six immediately identifiable factors; weather (W), debt (d), time since Christmas (T), time since failing our new year’s resolutions (Q), low motivational levels (M) and the feeling of a need to take action (Na).
The formula calculates that Monday 18 January 2010 is the worst day of the year, when the Christmas glow has faded away, New Year’s resolutions have been broken, cold Winter weather has set in and credit card bills will be landing on doormats across the land – whilst the January pay-cheque is still some way away.