At least according to psychologist David Holmes of Manchester University:
We each experience an average of 10 major happy days every year but none is happier than January 31, or Happy Monday. We all go into work on that Monday—January 31—with renewed vigor, buoyed by the excitement of having money in the bank again and having one of the major family events of the year—the annual summer holiday—to look forward to.
This time last year, the travel industry saw its busiest weekend of the year. But with all due respect to Dr. Holmes, it seems to us like people are just really ready to go somewhere warm. (Either that or the rest of the year is going to suck.)