time flows freely from one point to the next. envision the passage of time as a thick gel in an hourglass. let the standard concepts of chronology (seconds, minutes, hours, etc) represent a balanced environment, where the gel flows steadily from one end to the other.

however, when you're concentrating on something, deeply involved in work/play/whatever (in metaphor, pressure/concentration increases in the full end of the hourglass) then time always seems to move more quickly -- "my how time flies when you're ______ (fill in the blank)". time flies contingent upon the presence of the verb, or action (and so the gel is squeezed more swiftly into the other end.)

when there is no source of focus, when idleness sets in and you just keep looking at the clock, wondering how it can only be noon (in metaphor, when there is little or even negative pressure in the full end), then minutes drag on forever, and that little red second hand slows inexorably, dragging at life. (the gel is reluctant to flow to the far end, taking its time, taking its sweet ... damn ... *time*)