30 minutes after the official start of class...

...and our professor still is not here yet.

If this were the United States, the rule-of-thumb is that we would have been allowed to leave 15 minutes ago.

However, here, he may show up in ten minutes, an hour, or not at all, but we are expected to stick around in the case that he decides to hold class.

Oh, how I miss the American education system...