In The Magic Mountain, time is at once the subject and the form of the novel: in the sanatorium it stops running as it does on the plain, and habit and monotony shrink it until seven years pass almost unnoticed.
The idea appears from the arrival onward. Hans Castorp sets his visit at three weeks, and Joachim replies that three weeks amount to almost nothing "up here." Settembrini warns that there the smallest unit of time is the month. In chapter IV, the narrator interrupts the story with the Excursus on the Meaning of Time: years rich in events pass slowly, and boredom is a "morbid brevity of time, brought on by monotony." At the start of chapter V, with Hans Castorp in bed, the narrator calls this time of the bedridden patient "a now that has stopped," the same day repeated in which the soup arrives forever.
The book itself imitates the experience: the first four chapters cover the first three weeks, the narrator warns at the start of chapter V that the next three will pass in the blink of an eye, and in chapter VII the narrator asks whether it is possible to narrate time itself. In the end, Hans Castorp no longer uses a watch or a calendar.
The thesis holds outside the sanatorium: time shrinks where nothing changes, and the routine that protects is the same one that erases. What gives time back to Hans Castorp is not a decision of his own but a historical event from outside, the war.