I don't believe DR has centoes... but I could be wrong.
As for timing, the most recent TTD on my blog was done at sunrise (5:45 am)... and it was cold. However the sun rises over the water in RM, not sets. So that made a difference.
There is another TTD on my blog that is from noon.
I perfer TTD to be around 4pm. Less hot, less crowded, less tired!
You can really do them whenever you want, it just depends on your schedule, how long you have your photographer booked, and what look you're going for (morning sunrise pictures, bright color daylight pictures, golden sunlight afternoon pictures).