If time only flows in our perception, does it really exist?

I wouldn't say time flows only in our perception. It's true that our *experience* of time depends on how we perceive it, but there's solid enough evidence that time exists independently of us. Physical processes happen in a sequence: stars age, materials degrade, the universe expands. If time were only in our heads, these phenomena would have to happen simultaneously and randomly, but they don't.

What's more complicated is *how* time actually works. Modern physics has taught us that time doesn't flow the same way everywhere - it depends on speed, gravity, our frame of reference. But that doesn't mean it doesn't exist; it means it's stranger than what we learned in school. Our perception of the present, that's an illusion of our mind - the brain assembles information with a slight delay, so what we feel as "now" is actually always a bit in the past.

Bottom line, time exists as a property of the universe, but our relationship with it is filtered through perception. Two different things: time doesn't depend on us to exist, but the way we experience it depends entirely on how our brain interprets it.

Time exists because effects happen in sequence, whether you perceive them or not - perception doesn't create it, it reveals it. There's no point starting from quantum physics or Greek philosophy if the question is simpler than that.