Michael Flaherty explores the difference between the subjective impression of time’s passage, versus how much of that time has actually passed. The distinction is established between a reality of time, and contingent impressions of time.

Time flies. For centuries, this has been one of the stock phrases in Western civilization. But, on occasion, we are struck by the sense that time has passed even more quickly than is usually the case. This is to say that, in particular circumstances, it feels like much less time has elapsed than has actually been measured by the clock or calendar. Regardless of whether the relevant interval is ten hours or ten months, it seems to those of us in such circumstances that a much shorter length of time has gone by. Therefore, we can refer to this sensation as “temporal compression” (Flaherty 1999, 104).

Flaherty, Michael. 1999. A watched pot: How we experience time. New York: New York University Press.