Take a minute out of your day and make yourself infinitely smarter by watching this video. It explains how Albert Einstein discovered that our past, present, and future really all exist at the same time.
You see first Einstein discovered that speed and distance can affect your place in time.
That lead to the realization that if people at different distances and speeds can experience different times, then time must be constant and available always, for these people to be able experience it.
What will really bend you noodle, is trying to figure out if that means your life is already planned out!?