The best time to play is whatever time the weakest players are playing. In my opinion this means weekends and weeknights, which are the times when players might be doing sub-optimal things to hurt their games, such as drinking alcohol.
Of course, since poker is a worldwide game, if it is nighttime by you, it might not be nighttime elsewhere, so you can't just go by your own local clock.
However, for me, 7am east coast US time is a poor choice to play poker, because very few people are getting drunk and playing poker right after they wake up. LOL Adding 6 to 8 hours in order to see what time it might be in Europe, well its still only 1pm to 3pm and players there are probably still sleeping from last night's poker session.
So for me, 7am my time is a terrible time to try to play poker, I'll be playing almost entirely against other regulars and competent players which is not the optimal formula for success. It doesn't mean I won't play, I'll always play at any time because I love to play poker... but it means I won't be spending a lot of my
bankroll, I'll drop down in stakes and more-or-less just play purely for fun and for putting in hand volume so I continue to add to my experience in the game.