There are two main parts to timeliness to consider. Firstly punctuality, and secondly, doing things at the right time.
Punctuality
One hears many stories about the effects of being late. Missing the plane or train or missing the important appointment. In actual fact there is something rather more fundamental about being late and that is that it is just plain rude.
If you are going to a meeting, what message are you giving someone if you are late? You are saying that this meeting is not desperately important to me. I have not made any special efforts to be there on time. Something else I was doing was more important that coming to see you. More than that, it can cause problems with those you are seeing. They may have other things planned and your lateness means they have to cut the meeting short or turn up late for something else or even just spend less time doing something than they had planned.
Another aspect is that of your working time. If your work start time is 9am, it is simply not good enough to turn up for work at 9am. You are being paid to START at 9am, so need to be there before that so that you are ready to start at 9am.
The final point about being late is that you “antagonise” the other person. You start your meeting with them being unhappy or feeling negative. You are on a back foot before you start.
At the right time
Timeliness also means doing things at the right time. Get your invoices out when they are ready. Talk to the unhappy staff member immediately, don’t leave it to fester. Reply to your emails, even if only to acknowledge them. Get the customer order to the customer when you have said you would.
Effective time management is very important. It can mean the difference between success and failure. Getting it right won’t mean you always succeed, but getting it wrong will lead to problems.