There is no such thing to be found in nature.

As an ultimate fact it is a nonentity.

What is immediate for sense-awareness is a duration.

Now a duration has within itself a past and a future; and the temporal breadths of the immediate durations of sense-awareness are very indeterminate and dependent on the individual percipient.

Accordingly there is no unique factor in nature which for every percipient is pre-eminently and necessarily the present.
The passage of nature leaves nothing between the past and the future.
What we perceive as present is the vivid fringe of memory tinged with anticipation.