Yep. I know what that's like. I'm so sorry that your parents yell at you because of it though...that is not right.
What helps me is to pretend like you have to be somewhere 10 minutes earlier than you actually do. Like they tell you to be somewhere at 8:30 but you just pretend that they said 8:20 instead.
Also, the time that you have to leave for something, give yourself a few extra minutes to get out the door. For example, to be at school on time I need to leave at 7:40. But I always tell myself that I need to be out the door by 7:30, and that if I leave at 7:35, I'll be late. I definitely helps. Because it always takes more time than anticipated to get out the door.

Hope that helps some!