What you think of as the past is a memory trace, stored in the mind, of a former Now. When you remember the past, you reactivate a memory trace — and you do so now.
The future is an imagined Now, a projection of the mind. When the future comes, it comes as the Now. When you think about the future, you do it now.
Past and future obviously have no reality of their own. Just as the moon has no light of its own, but can only reflect the light of the sun, so are past and future only pale reflections of the light, power, and reality of the eternal present. Their reality is “borrowed” from the Now.