If you're early, you're on time,
If you're on time, you're late,
and if you're late, it's as if you were never there at all.
You've probably heard some variation of the above at some point in your life. The importance of time management cannot be emphasized enough. In your personal life it should be important, but in your work life it is important without exception.
If a meeting is scheduled to begin at 9:00AM then believe that it will start at 9:00AM. The question is, will you be there before it begins? You don't want to walk through the door for a 9AM meeting at exactly 9AM. Don't do it. Let's say you do, then that means you are walking into a meeting that has begun, finding your seat, pulling your chair out, getting settled while someone is talking. Even worse, you do this and the entire meeting waits for you to get settled before continuing. Now you've drawn attention to yourself and not in a good way. Make sense? So try and get to a meeting at least 5-10 minutes early.
Now if you have an interview, you definitely need to arrive early. No question. Some interviewers will have paperwork for you to complete and will ask you to arrive early to complete that paperwork. If they do not say anything, you still need to arrive early (I'd recommend 10-15 minutes).
Murphy's law says that not everything is going to be in your control. Sometimes things just go wrong. There are an endless list of possibilities but let's go with the most common one to affect people. Traffic. You were smart and left early and even gave yourself cushion time to arrive where you're going. If you're going to be late, have the courtesy to call and let someone know that you have been unavoidably delayed. And by someone I mean whoever you are meeting. 🙂 It is better for you to call and let them know you will be late rather they find out when your appointment/meeting time has come and gone without you there. Shows you have some foresight, sense, and respect for their time.
Try and carry this over into your real life. Showing respect for someone else's time, can go a long way in showing that you respect them. It also says a lot about you as a person.