I'm in the CEST (Like CET, but set for summer daylight-savings time) timezone, and tend to be most active on the forums.... all the time.
I'm active from about 07.00 in the morning local time to about 15.00 in the afternoon, with a break for lunch, and then I usually take a few hours off, and come back to be active in the evenings, from around 18.00-21.00. Unless I fall asleep on the couch and forget all about it.
For reference, 07.00 Swedish time is about 10 PM PST, if I've got my timezones right.
I've got most of my followers active either during my lunch hour, or during the night when I'm asleep, so I'm assuming their either scattered across different timezones, or they're night-owls.