According to a study by a sex toy company, next Tuesday . . . December 11th . . . is the most fertile day of the year. They looked at birth records and found that September 16th is the most-common birthday . . . and most of the people born on that day were conceived about 40 weeks earlier. Experts said that it could be because people feel more festive in December. (--CAREFUL!) And also because, supposedly, man-seed quality is higher in cold weather.