Everything that you are experiencing now is your brain’s perceptions of them, it may not be real. That is why hallucination is pretty much ‘visible’ to only that one guy.
Many articles available online to explain these things but many people are still not aware of it. So I just dig a little more and try to find the history and logic behind it. Why 12 months in a year? Why 24 hours in a day? Let’s have a look at it.