The two best times during the week are 10:00 am EST and 6:00 pm EST. By 10am, the east coast has finished their email and incoming snail mail and want to see what's happening on steemit. Western Europe is winding down their day, yet haven't left work, maybe.
6 pm EST, east coast US is home from work, or nearly, and western Europe is still on the interwebs.
4pm-5pm EST is the absolute worst time to post. Commuting on the US east coast. nuff said.
On the weekends, material has to be out by 1:00 pm EST or you're writing for crickets.
Excellent point, thanks @wakeupsheeps!