The basic unit of construction in the theatre is the scene, and the amount of dramatic time that elapses during a scene is roughly equal to the length of time the scene takes to perform. To be sure, some plays cover many years, but in general these years pass "between curtains." We're informed that it is "seven years later," either by a stage direction or by the dialogue. The basic unit of construction in movies is the shot, which can lengthen or shorten time more subtly, since the average shot lasts only ten or fifteen seconds. Drama has to chop out huge blocks of time between the relatively few scenes and acts; films can expand or contract time between the many hundreds of shots.