If you make an appointment with someone for a specific time, or you are going on an excursion, you are expected to be there at that time. People may be early or, in some cases, late. Call if you are running late. In the US you will be considered late, extremely rude, and the other party will be gone. Classes and worship services begin on time.
Weddings traditionally begin with the minute hand going up past the half-hour.
The importance of being on time cannot be stressed enough. The earth is divided into 24 time zones extending from the north to the south pole. Four of these time zones are located in the United States. Each zone is one hour different from the adjacent zone. If you want to know what time it is before calling home, you can use the International Time Zone Map in this handbook or you can find the Time Zone Map in the Directory of the telephone books from Bell South.