Many people have tried 5am est since certain time zones are already awake that carry large votes.
Outside of that it is dependent on your audience. Many post at different times of the day testing out what is there best time zone.
I forget name of a app/site that would find this data for you and suggest times to post.
I just post when ever I get around to it. Not the best idea.
steemian spreads out your post to when you want them published