Here are the results for the timezone evaluation:
# of Participants: 9
GMT -0 (UK): 2
GMT -5 (EST): 5
GMT -6 (CST): 1
GMT -8 (PST): 1
Best Days of the Week to host an Event: (in order)
Varies Weekly: 4
Optimal Time to Host Events:
Generally speaking, the survey takers are most active
between 7pm GMT/ 2pm EST / 1pm CST / 11am PST
and 5am GMT / 12am EST/ 11pm CST / 9pm PST
The two best hours are
between 8pm GMT / 3pm EST / 2pm CST / 12pm PST
and 10pm GMT / 5pm EST / 4pm CST / 2pm PST
What does this mean?
In summary, to make an event that is during a time when players are most available to come, you should make it on one of the weekend days in the afternoon/night-time, regardless of what timezone you are in. However, there are a few things that need to be considered.
1) This is by no means the most accurate or valid survey. Only 9 people took it out of what I would estimate to be around 20 active members that check the forums regularly (high balling).
2) Just because there is an event at a time where people are available to attend doesn't mean they will. They still have to actually be interested in what is actually going on during the event.
3) This can and will change with time, and may already be outdated to some degree (with Uni finals being around now/next week). This is just a super general, semi-educated guess.
One would also assume that these times would also work for events that are not on Runescape specifically, because I don't really know anyone who has carved out hardcore Runescape time into their daily/weekly schedule (but who knows). I hope this helps a little bit with figuring out a good time to host an event if you choose to create one.