When's the best time to negotiate?

According to studies our peak mental agility occurs 2-4 hours after waking up.

After that our willpower slowly leaks away.

Carl Icahn - the U.S. billionaire investor - schedules his negotiations to start at 6pm. He sleeps until 4 in the afternoon. Those sitting across the table from him at the start of the negotiation are already exhausted from a full day in the office, but Carl is fresh as a daisy.