Hi @grishka,
personally I like 'human readable', coarse times consisting of only 2 parts and a single granularity: a few digits (max 1 decimal) + unit. But I consider the full fine data down to the second as e.g. tooltip (html title attribute) mandatory.

It's a matter of taste. To decide, (I) always do (say: try) a #UX #test with a number of real people.