In the United States, it is not customary to telephone someone very early in the morning. (在美国通常不会在清晨给人家打电话。) If you telephone him early in the day, while he is shaving or having breakfast, the time of the call shows that the matter is very important and requires immediate attention. The same meaning is attached to telephone calls made after 11:00 pm. If someone receives a call during sleeping hours, he assumes it's a matter of life or death. The time chosen for the call communicates its importance. In social life, time plays a very important part. In the U.S.A. guests tend to feel they are not highly regarded if the invitation to a dinner party is extended only three or four days before the party date. But it is not true in all countries. In other areas of the world, it may be considered foolish to make an appointment too far in advance because plans which are made for a date more than a week away tend to be forgotten. The meaning of time differs in different parts of the world. Thus, misunderstandings arise between people from different cultures that treat time differently. Promptness is valued highly in American life, for example. If people are not prompt, they may be regarded as impolite or not fully responsible. In the U.S. no one would think of keeping a business associate waiting for an hour, it would be too impolite. A person, who is 5 minutes late, will say a few words of explanation, though perhaps he will not complete the sentence.