From Slashdot:

RonMcMahon writes "Dr. Arnalls from Cardiff University has crunched the numbers and has precisely determined that Monday, January 24th will be the worst day of the year. For those of you who might be wondering, the formula to use when deciding what day to stay in bed is 1/8W+(D-d) 3/8xTQ MxNA. The fact that the 24th happens to land on a Monday is purely coincidental."