ADHD patients are constantly late. It is a big problem when they study at school or go to work. Because of this problem, ADHD people often receive low grades and/or get fired. They may be late even for the most important events in their lives such as a wedding, child birth, and so on, which may lead to the worsening relationships with spouses, friends, and relatives. They do it unintentionally, being unable to estimate the time required for certain activities.