A friend assigned to Stockholm was told that the Swedes expected promptness, so on their first dinner invitation, and uncertain of the way, they left home early. They arrived five minutes before the appointed hour and found four other guests standing silently in the hall outside the door of the hosts' apartment. At exactly 7 p.m., the guest closest to the door pushed the bell. The door opened immediately, and all six guests filed in together. We recognize that a doctor's appointment is only an approximation.
T here are also regional differences.
After some years in North Carolina, I think most Southerners would find the Indonesian approach to time less strange than I did.