Not only does the time of your birth matter, but also the location.
Have you ever noticed that the night sky looks different if you travel to a faraway place? Or that the Sun rises and sets at different times, depending on your location? Not only does the time of your birth matter, but also the location. Where you were born determines what the sky looked like when you were born, and therefore what your birth chart looks like, and what it has to say about your purpose.