When formatting timespans in short form for something like a stopwatch, I know the standard in most places is to use
hh:mm:ss.ff (where "f" is "fractional second"). Some places will use
mm' ss" ff, which is also okay.
What about days, though? I've never seen a consistent standard, or such a thing being used much (currently I use the longhand,
ddd days hh:mm:ss, but I think that looks ugly because the days get disproportionate spacing). What ways are there of doing it? Also, when using
mm' ss" ff, what do most people use for hours?