Why ask a forum which is better answered by a simple time chart with a volume indicator?
High Volume > Low Volume = Preferred Trading time.
It isn't that much different than trading stocks [ref: preferred trading hours.] Pre-market 4:01 AM isn't the most preferential time to be trading stocks.
Just as OEX, FOMC, Employment numbers, Petroleum reserve reports provide high volatility. Depending upon trading style, may or may not be considered preferential time's. Experienced trader they can be absolutely wonderful, for everyone else catastrophic.