With almost no experience, newly graduated medical students enter teaching hospitals around the country every July, beginning their careers as interns. At the same time, the last year's interns and junior residents take a step up and assume new responsibilities.
In addition to developing their nascent clinical skills, each entering class of interns must grasp the many rules and standards for operating in this "new" hospital structure.
More experienced physicians share a joke about this changing of the guard: Don't get sick in July.