Being late tells the person you’re making wait for you that you don’t care about his or her feelings, and that you don’t respect their time. It lowers their opinion of you.
If you know you are going to be late you need to be honest with the person you’re meeting, as soon as you realize that you’re not going to make it on time. If its 7:15 and you know you’re not going to be able to get there by 8 that’s when you need to send a text apologizing and be honest about what time you’ll actually get there. It’s considerate and your date will appreciate it so he/she can adjust their time accordingly. She may be running late too and can utilize the extra time. You’ll make a much better first impression and you may even get extra points for being thoughtful.