Blue Monday

According to this proven formula, the 3rd Monday in January is the most depressing day of the year. Hmmm, not so sure. Where 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. 'D' is not defined in the formula though, maybe it means 'drivel'.