The problems people have with time is that we can't see it. With 3D we can actually see it, and interact with it. With 4D, humans cannot actually 'interact' with time, we have only knowledge of it passing us. We cannot even see it so to speak, we can only see the consequences of time. But it does exist. The consequences are there to see. For 3D, we can interact with it, and see the consequence, so it is easy to believe. If we throw a ball, the consequence is that it moves.
Interaction: throwing.
Consequence: moving.
We cannot move through time, we cannot interact with time. But we can observe the effects of time.
Interaction: None from humans.
Consequence: Objects changing.
This is why we have to create artifical ways to see the fourth dimension; ways in the form of measurements.

__________________

Thanks to Lady Knives for the fantastic signiature and avatar set!
Epic Flan - XBox Gamertag (if you add me, tell me who it is in a message!)