What is time?

Is “time” a universal truth? Consider one of my favourite films, Interstellar, where Matthew McConaughey finds himself in a tesseract; this was an incredibly difficult concept to capture on film, and I think it was done really well. Effectively, this is a 4-dimensional space where the 4th dimension is time. In other words, all time is simultaneous and where we are at one particular ‘point’ in time is not a necessarily “mutually exclusive” event. As Rovelli expains it – the universe is made up of countless events – even something trivial such as a rock, is an event which takes place at a rate which we as humans cannot process!