If we accept Einstein's General Theory of Relativity, the past, present, and future are happening now. Time is a property. But we experience it as a logical succession of events. We have developed brain clocks to measure linear time. 

There are interesting considerations about time to do with freewill, action and consequence - themes raised in HG Well's Victorian science fiction. But there's also the issue of morality. The necessity of Time's Arrow moving in the direction that it does. The exchange of innocence and experience. This insight is a gift of Martin Amis's short novel Time's Arrow and complimentary to the ideas of astro-biologists like Paul Davies, who argue that for human life to exist as it does, the whole universe must be as it is. 

Time's Arrow opens like this:

I MOVED FORWARD, out of the blackest sleep, to find myself surrounded by doctors... American doctors: I sensed their vigour, scarcely held in check, like the profusion of their body hair; and the forbidding touch of their forbidding hands - doctor's hands, so strong, so clean, so aromatic. Although my paralysis was pretty well complete, I did find that I could move my eyes. 

Tod T. Friendly is born on his death bed. Events are narrated backwards by the playful, child-like innocent conscience of Friendly - an ex-Nazi doctor. With Time's Arrow running backwards: violence heals, death precedes life, and the tragedy of Friendly's evil crimes are startlingly revealed. 

The reversal of linear time presents real challenges to our sense of meaning. Wrong becomes right. Massacres are frenzies of life. But then, perhaps, linear time is a necessary illusion. And, as TS Eliot speculated in the first of his Four Quartets:

Time present and time past
Are both perhaps present in time future,
And time future contained in time past.
If all time is eternally present
All time is unredeemable.
What might have been is an abstraction
Remaining a perpetual possibility
Only in a world of speculation.
What might have been and what has been
Point to one end, which is always present.