Many/most futures markets trade 24-hours now in some fashion. ES in particular does so. The primary session runs 08:20 to I think 16:00 ET. That's where the bulk of the volume takes place. It's during any given market's primary session where you will generally see the U shape volume distribution.
jjanguda, I find for the futures you have listed the best time is an hour before premarket and up to midday EST. For 6E and other currencies the same goes for the FTSE open, best time is an hour before premarket and through to midday EST. That is when most of my trades start and finish.