Firstly, Davide has implemented a system for querying the servers to display graphical information about high usage times. I can't recall the actual command to use, but it's either in the automated display message when you first connect to the server, or Davide will likely see this thread and naturally let us know here
Secondly, I usually play my GT games early in the morning when I can focus without too many interruptions. My time is GMT -05.
Finally, it's pretty rare that I have 2-3 hours to spare to play a good game online. The last game we played together, you and I, was quite fun but we started a bit late and I remember you had to leave just as things were about to get really interesting
Still, sometimes I can spare a game in the afternoon (between 2-5) and occasionally in the later evenings (between 8 and midnight).
Hope this helps. By the way, El_Perdedor logged onto the server we were playing a little while after you logged off. He gave you a good compliment, saying that you've been playing better and better lately. Keep it up!