It would make sense if the fastest times ever show in ranked order on the various leaderboards until those times are bested. Is that true?
Welcome to the forums @R_Rocket_R_Gruppe
That wouldnt really make sense as you would only ever have the top 000.1% of Zwifters showing, and then the vast majority of people wouldnt bother trying.
If its overall live results then 60mins, but leader boards show your previous 30day efforts too. More here