What is the biological function of time?
There's at least one.
Which is that it keeps things open. It prevents horror from being permanent for the one for whom it matters, the conscious one.
Because experience seems to be tied up in time, it means that there is the possibility of something different, of something better.
There is some idea that time may not be fundamental. That the structure of how things are is geometric and that time itself is determined by the relationships between elements of this geometric structure; somehow our experience of time, somehow, experience, is such that atemporal relationship is translated as a one way arrow.
This only underscores the importance of the question of what consciousness "is."
I say what consciousness "is." "Is," with quotation marks, tells you about my uncertainty, because the boundaries between is and is not for consciousness (as well as everything else) are fuzzy. One reason they are fuzzy is because of our experience of time. "All the time,” we experience things becoming other than what they are. We might want to say that that's what consciousness is. The relationships between geometrical elements, this betweenness, is time.
That brings us back to biology. Why is time, and consciousness, necessary for biology? Why biology at all? Maybe the difference between biology and non-biology, between life and non-life, is not really that important.
If we think that, somehow, there never was a was without time, and there never was a time without consciousness, then the meaningful difference between biology and non-biology doesn’t exist anymore.
So what is time's function for biology? Perhaps biology, time, consciousness, and the relationships between elements in a geometry are the same thing.
The way things are is such that the way things are and the way things are not is fuzzy, at least that's what it seems like so far, to me.