“Time is a human contrivance.”
That’s absurd. The language we use to describe time is a human contrivance, but not time itself.
Nature has always been all about change, and when things change, there is a “before” and an “after”.
Time is change - change is time - humans may be the only ones that talk about it, but all things in nature experience it.
The reason your dog is so happy to see you is that it has been a while since you left. Dogs think in “whiles”, humans keep track of hours and minutes - the only difference is the language.
The reason your grass grew longer is because it has been a while since you last mowed. The grass may not be conscious of time, but it experiences change, and therefore the passage of time.
Change is not identical to time. Time is a mathematical structure invented to categorize change.