Modes of time in terms of their potentialities for knowledge and action: without the present there’s neither past nor future so much so that past and future can’t be understood except as modes of presence.
Past is the knowable but unchangeable present.
Future is the changeable but unknowable present.
Now is the knowable and the changeable present.
The present reality is not a temporal consequence of a past, neither preceding an inevitable future.
Viewed phenomenologically, that is, from above and within, the past and the future are ontological moments of a living present, and hence owing their apparent reality to the actual reality of the now.