You are trying to define timelessness (“now”) in terms of time which does not compute.

To the intellect everything happens on a canvas of time, with “I” being a mere fleeting object among other objects on that canvas. In that mental coordinate system the “now” appears to be an inconceivable boundary between past and future, hence without particular importance.

In awakening things shift quite dramatically: The “relative” (biographical/imagined/false) “I” is realised as a fiction, revealing the “absolute I” ("God, buddha, consciousness, emptiness, Self"). The relative now (imagined slice of time) becomes the absolute now (timelessness, "this"). Past and future are seen as merely practical phantasies without descriptive or psychological power. Life loses its linearity. Everything just happens on the canvas of “now” which is “I”.

I admittedly struggled for years with Tolle’s mantra of the “now” until I got a first-hand glimpse of it.