Every single administration of the test that I have looked into has set it at 8am local time. I've taken it twice, in 2009 and 2011. Perhaps things have changed since then though. When you book your test, it will tell you the time though.
Note a few useful logistics things:
1. Locations may change at the last minute. At my second exam, it was listed at some building on a University campus. When I got there, there was a sign saying it's in [other building name]. Since it was not my university campus, and it was Saturday morning, I had no idea where that was and it was hard to find the new place. Luckily I had arrived 1 hour early so I had time to figure it out.
2. All the subject exams happen at the same time in the same place. So the room will be filled with exam takers of all subjects!