Looking in history, June 3, 7am CET it was. Just 6am UTC. Txs were below 10 per hour these hours, i was looking for NEMstake price in NXT wallet and i noticed this number. This means probably that most of NXTers are Americans. However we are a bit off topic.
When NXT gets more popular in Asia, those early Europe morning hours's blocks would also be filled, for now it's best to look at daily volume and average txs per hour number.