There is a considerable degree of structure to the timeline and application process in the academic job market. By contrast, job markets beyond academe are much less structured; turnover and growth occur throughout the calendar year. That being said, some large companies in certain industries (e.g. finance) conduct a great deal of hiring in the fall, especially for entry-level positions, with the goal of bringing new hires on board for formal training programs in the summer. Varying hiring patterns give you all the more reason not to put off researching careers and employers that may interest you.