Hard to grasp two contradictory dimensions of Time: the relative and the absolute.
On the one hand, time seems to be a finite flow from past to present into the future... filled with memories, fears, hopes, plans. The continuous 'if only' of the regretful backward glance; the perpetual 'what if' of our ambition. All just mental processes - a world of thought. Therefore unreal.
On the other hand, time itself is infinite and always present: eternally, inescapably, simply 'now'.
Sitting zazen, there's truly no such thing as time. Experientially, everything is comprehensively contained in this moment of zazen. Past, present, future... all contained in 'here and now'. What else could it be? Where else could it manifest?
Now/here (nowhere) is the only thing we directly experience; but even that is not cradled in our usual concept of space/time. Just as you reach out to grasp it, it's gone. There's nowhere to put your hand. Where does the sea end, the wave begin? Where does your fist go when you stretch out your fingers? Language tricks us at every turn.
There's nothing for it but to let it go; to float at ease in the timeless present...
Going, going, going on beyond, always becoming Buddha. Hail! Hail! Hail!