What time is it?

If past and future are private/social constructs and the present is ungraspable, how do we understand time? It's so easy to think of time as passing us by or passing quickly but aren't we right here in the river with it, as it?
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Nagarjuna (150-250 CE): "Time has no concrete reality."
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Robert Aitken Roshi (b. 1917 CE): "Time and no time, substance and the void, existence and nonexistence - these are the traditional dyads of the human program. With zazen we find the Middle Way and the hoary concepts of dimension drop away."
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Bob Weir (b. 1947 CE) of the Grateful Dead: "What I like best about music is when time goes away."