Not a model,
If you look at some of the traffic ranking sites,
USA might make up 35% - 40% of traffic.
Canada 5% - 9%
UK 5% - 9%
Germany 4.5% - 6.4%
8pm EST is 5pm PST as in, most people in the USA are home from work. You also have similar traffic from Canada 5%, and south america.
10pm EST is 7pm PST
12pm EST is 9pm PST, your loosing loosing east cost US / Canada, but it's now 6am germany. So your getting Germany morning traffic.