I've been wondering about Peak busy hour at WGT for a while and decided to do some research on internet traffic patterns just to see how many players are affected by the WGT maintenance interval. I found this article about European traffic patterns vs North Americans.
I added info to their graph to make it more relevant to WGT.
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I figure North America plus Europe is roughly 75% or thereabouts of WGTs total traffic. Based on that WGT has chosen the time of their shutdown in order to minimize the impact on players. 11pm to 2am Pacific time is the lowest traffic period on WGT.
At the other end, it appears 8am to 3pm Pacific time is probably the highest traffic on WGT.