If you’re looking to prove yourself to clients, coworkers, or anyone else, Karl Erickson, a former Green Beret Sergeant Major, says that there’s one key thing to do that shows you mean business — be on time.

The great thing about being on time is that it doesn’t take weeks to make a good impression, like it does to impress people through your hard work. People immediately notice when you show up on time, and it creates a positive first impression.

Of course, Erickson learned the importance of promptness during his time in the armed forces. While in a hanger with a helicopter pilot, he saw that the wall had a message saying “Plus/Minus 30 seconds or Not at All.” When he mentioned it to the pilot, that pilot explained to him that no matter what the situation on the ground is, if the helicopter is supposed to be there at a certain time, it will be there at that time.

Being on time may not be a life or death situation for you like it is for those in the military, but it’s still one of the most important parts of making a good impression. When you’re on time, people consider you reliable. If you’re late, people consider you unreliable and unprofessional. It gives them the impression that you don’t value their time.

What about being early? This can be just as problematic as being late. If you show up 10 minutes early to a social event or a business meeting, you might be there before the other person is ready, which can annoy them. It also demonstrates that you don’t value your own time, because you’re willing to sit around waiting because you got there early.

You probably know how frustrating it is when you hire a contractor or another type of service provider and they show up 20 minutes after they said they would. When you find someone who shows up on time to the minute, it starts things off on the right foot. You’re more likely to hire that person again, because you know you can trust them to show up when they say they will.

Apply the same concept in your own life and see how it changes the way people perceive you. Other people may even comment on your promptness. Not many people make it a point to show up on time. When you do, you stand out from the crowd.

Originally published at medium.com