My view is that time is not fundamental. It's just a function of physical things happening
(e.g., physical change). If there were absolutely no physical change in the universe, there would be no time. This explains why time is moving irreversibly from past to future: because things keep happening. To go from future to past, there would have to be a reduction in the number of things, or events, that have already happened in the universe. This doesn't occur. This seems to go along with what they said in the video that clocks count ticks (physical events) and the count gets irreversibly bigger.
Many physicists think that because they can change the t (for time) variable on their paper from
positive to negative and the equation still works, they think that time itself should be able to go backwards. But, an equation is not the same as time. As above, time can't go in reverse because you'd have to reduce the number of physical changes that have happened in that system, and you can't do that.