First of all, when I brew at my friend's house, we usually start firing up our systems around 10 am, and start sampling beer at 10:15 am. I seems like enough time for the coffee taste to subside from the drive over.
Secondly, my wife and I honeymooned in Ireland last May, and our original flight was cancelled due to the volcanic ash cloud. We caught a flight the next day, but we had a stopover in Frankfurt on the way to Dublin. We had just enough time to grab a hefeweizen and a pretzel in the airport, so we couldn't resist. For the record, it was midnight EST, but 7 AM in Frankfurt. No one blinked when I placed my order. So I agree, it is a combination of your biological clock and the culture around you.
Joe