Narnian Time

"It's the usual muddle about times, Pole."

- Eustace Scrubb to Jill Pole Narnian Time is a term commonly used to refer to the passage of time in the world of Narnia, as opposed to the passage of time on Earth (with England as the usual place of reference).

Relative timelines
In Narnia, time did not feel any faster or slower than on Earth (for example, a year in either world took three hundred sixty-five days); however, the relative speed of Narnian time to Earth-time was inconsistent and erratic. When one was on Earth, there was no way to tell how quickly Narnian time was going. Between the Birth of Narnia (Earth year 1900) and the Pevensies' first visit (1940), forty years passed on Earth while a millenium passed in Narnia. Between the Pevensies' first two adventures in Narnia, one year passed for them on Earth while nearly another millenium passed by in Narnia. At another time, a week on earth passed in only ten minutes of Narnian time. Also, however much time an inhabitant of Earth spent in Narnia, no time passed in England. For instance, during the Golden Age of Narnia, the Pevensies (Susan, Edmund, Peter, and Lucy) reigned in Narnia for fifteen years. However, when they came back to England, their whole adventure seemed to have taken no time at all, and they were back at their previous ages.

The entire Narnian timeline, from its creation to its end (1–2555), ran parallel to 49 Earth-years (1900–1949).

Effects on visitors from Earth
Some of the skills and maturity the Seven Friends of Narnia gained in Narnia seemed to disappear when they returned to Earth. For example, Lucy learned to swim during her reign in Narnia, but she could hardly swim at all after she went back to England. The same effect seems to have occurred with emotional maturity, although it is unknown to how great an extent.

It is apparent, however, that going back to Narnia gradually returned to the children the maturity they had gained on previous visits. For example:

"I don't think Edmund would have had a chance if he had fought Trumpkin twenty-four hours earlier. But the air of Narnia had been working upon him ever since they arrived on the island, and all his old battles came back to him, and his arms and fingers remembered their old skill. He was King Edmund once more."

- C. S. Lewis, describing the fencing match between Edmund and Trumpkin