Time past has taken all the pap and pain-killer and sawdust and bicycle-wheels and tides and nature. The past is gone. The future is not yet. The present moment is the only space for existence. And it is always the present:

Hamm: ... What time is it?
Clov: The same as usual.
Hamm: [Gesture towards window right.] Have you looked?
Clov: Yes
Hamm: Well?
Clov: Zero.

Change belongs to the past and to the future (and they belong only to the memory and imagination). One cannot live in the past or in the future. The present can never finish, though the closer to the future, the more 'nearly finished' may be present time.

'Endgame' begins:

Clov: [fixed gaze, tonelessly]: Finished, it's finished, nearly finished, it must be nearly finished. [Pause.] Grain upon grain, one by one, and one day, suddenly, there's a heap, a little heap, the impossible heap.

and near its end:
Hamm: … Moment upon moment, pattering down, like the millet grains of ... [he hesitates] ... that old Greek, and all life long you wait for that to mount up to a life.

The mention of the grains of millet and 'that old Greek' are allusions to one of the paradoxes of the fifth-century philosopher, Zeno. If you pour half of any quantity of millet seed into a heap, Zeno reasoned, and then add half of the remaining seed on to the heap, and so on… then the nearer you get to completing the task the slower the heap will grow and, in fact, the heap can never be completed (not in any finite time scale).

As the moments of living heap up, the nearer it is to life's end but the slower present time will pass. The catch is that enduring the increasingly contracting yet ever-lengthening, infinite present is the only means of waiting for the unknown (and perhaps unattainable) future.

So the time is always 'The same as usual' and every day is 'a day like any other [bloody awful] day'. Hamm is left ever asking for his pain-killer and his coffin and his suffering to end ('with a bang!') and Clov can only threaten to leave, while the present tide and light and weather can only remain the same as now. Change is beyond the present, static moment.