Sun Online says today, Monday, January 24 is the worst day of the year:

“The calculation is based on: The poorest WEATHER – which tends to be around the middle of the month; DEBTS owed after the seasonal spending spree; the TIME since Christmas; the period of time before you QUIT New Year resolutions; the dates when MOTIVATION levels seem to be at their lowest; and the timing of a NEED FOR ACTION to escape the blues, like when you book a holiday.”