Thanks everyone so much for your inputs.

BranShea, yes, stretchability is certainly implied in 'time span'. 'A space of time', on the other hand, points to a desire and struggle to elevate the subjectivity of experienced time to a more or less objective fact. Or phenomenon (!): I've been thinking that there is not a single better illustration of the phrase than cinema - its temporal duration arises out of the space that frames cover. Could experienced (subjective) time get any more objective?

I've only read the phrase in Dickens - 'Oliver Twist'. But maybe it dates further back...