It is important to define start time but even after defining start time for everything we still almost every time are running late because we don’t define the end time. Even when we define the end time, we don’t stick to it. People who are strict about start time, aren’t equally strict about the end time. If you want to get time to be able to do things that you want then define the end time of your meetings.
Define the time to leave the office. Define the time to hit the bed. Define end time to everything you do and that will complete the time integrity.
When you define the end time, you will be more productive as you would be focused on completing the task.