The self-adjustment of the mind in the attitude of expectant attention proves again and again to be vain and futile, and it is this fact which brings home to it the slowness of the sequences of perceived fact, as compared with the rapidity of the sequences of imagination.
When speaking of the retrospective estimate of time, I observed that the apparent distance of an event depends on our representation of the intervening time-segment.

And the same remark applies to the prospective estimate.

Thus, an occurrence which we expect to happen next week will seem specially near if we know little or nothing of the contents of the intervening space, for in this case the imagination does not project the experience behind a number of other distinctly represented events.
Finally, it is to be remarked that the prospective appreciation of any duration will tend to err relatively by way of excess, where the time is exceptionally filled out with clearly expected and deeply interesting experiences.

To the imagination of the child, a holiday, filled with new experiences, appears to be boundless.
Thus far I have assumed that the date of the future event is a matter which might be known.

It is, however, obvious, from the very nature of knowledge with respect to the future, that we may sometimes be certain of a thing happening to us without knowing with any degree of definiteness when it will happen.