Well, first of all, what exactly is time? People have been saying to me for years that time doesn't really exist. It is but a concept we have created that no other life form lives by. We invented clocks and labelled time with hours to organise our day. But surely that's just a measurement of something that already exists? We do exist in a 4 dimensional space, don't we? You can measure something by it's first 3 obvious dimensions and by it's measurement in time? A dimensions that, like the other 3, is ever expanding as the universe spreads out across both space and time? And you can use changes over time to chart courses between objects and objectives? But we know that if we do this, we can see discrepancies between the objects from the perspectives of the observer and the traveller - and this becomes ever more apparent across larger distances and higher speeds in an effect we call temporal dilation. What then are we witnessing? The passage of time or the slow and inconsistent degradation of particles? The entropy of the universe. Whatever it is, we clearly see this effect around us and we call it time.
What do philosophers mean when they say no other animal lives by the concept of time as we do? They live by day and night as we do. Psychologically, I've read that animals like dogs are unable to connect cause and effect over time on the same level that we do. But isn't that just because we think deeper about a concept that they understand on a more simplistic level?
But that still doesn't answer the question. How do we think about this time thing in a way that differs from other animals? I can't say I truly understand how a dog's brain functions, or even other peoples', but do I know how my brain does it. The first existence of an object or event in our 4 dimensional reality is in my mind - it will exist or occur and I think about it. Unless I'm unaware of it, obviously, but it is still going to exist primarily. Then it occurs in the present. Finally, it has past behind our linear perspective and becomes the past. It then exists in the past for as long as memory of it does. So the simple answer, in my opinion, is future-present-past. Our brains work in the opposite way to linear time motion in order to allow us to continue forward and analyse our past, only in order to continue to plan the future and move forward.