Perhaps, instead of modern contemporary philosophy, try explaining it to the present modern you. If you can explain it to yourself, then it is philosophy.
Well, the present isn't the past, is it? The past is the past. The present is the present. And the future is the future. They're mutually incompatible properties.
Something that exists now, is in the present. It may have existed in the past - but that's not the same as saying that it exists now. — Bartricks
Past, present and future, or linear time as I have learnt to call it, is fundamentally dependent upon our 'refresh'-rate. That is, how many times we need to do (perform) or relay influence over our faculties for perspective to be generated, developed/cultivated and permanently set (crystallized) within us. The intelligence which operates within reality is continuous throughout infinity/eternity. That is, for reality (the absolute or God), everything is one continuous active moment of intelligent application. For us, humans, the 'refresh' rate is quite short. For example, we cannot endure more than a few minutes without oxygen or a few days without sleep, we cannot carry memory from the first moment of our breaths to our last, to cultivate any kind of discipline within us takes many cycles of repetitions, we have a life cycle of about 100 years, and so on. So, it may be said that, in terms of application of intelligence, the greater the 'refresh' rate the lesser the intelligence a particular point of reality applies.
Think about it this way, why do we say that our reptilian brain governs our survival mechanism. Perhaps, it's because, in one perspective, the reptilian mechanism of physical life is superior to any others. Even today, reptiles are some of those with the longest life-spans. So, it could not be coincident that, through all our life evolution, that part has been maintained.
Anyway, my point is this, we have a past, present and future, or whatever other designation of time, because the processes of intelligence which we apply need to be reset every so often. This way, when we sleep, nature's intelligence (mechanism) takes over, and when we wake, our activities are a combination of nature's intelligence and ours. For us, time is a better marker of relativity and activity than our memories.
Another consequence of the refresh rate in our application of intelligence is the size of our consciousness (awareness-response mechanism). For example, I'm currently alone in my study. Suppose, one of the people I know dies right now. By the time I'm informed about it, the event would be in the past. And, before being informed, the concept of that life would still be in my present, eventually to be revised much later after the fact. However, if a significant part of your body dies, you will be in the know throughout the whole process of its demise. But, the intelligent mechanism making that possible is one designed by nature (reality) for us.
Therefore, it is our limitations that organize sequences of events linearly through pasts, presents and futures. And, it is possible, with unlimited application of intelligence and, consequently, an unlimited consciousness (awareness-response mechanism), to conceive of reality (in its absolute sense) as only having a now. Because all activities are contained within that single enduring moment.