Time is an illusion.

Reason: Think about yourself right now. You exist (or at least something exists - your senses, thoughts and feelings). Now imagine that time somehow made this disappear. But if you already concluded that something exists, how could it also not exist somehow, because of time? Things either exist or not, it's a binary choice, so how could time make something that clearly exists also not exist?

So, time has to be a fourth dimension, akin to the block theory of time. Each moment is located at a certain position at in time, but all these moments exist equally. We just can't travel between these moments freely.