http://www.youtube.com/watch?v=A3oIiH7BLmg
In that vid, there are basically 6 modes that people live in.
1. past negative - remember only the bad things (catholic)
2. part positive - remember only the good things (catholic)
3. present fated - no use planning, it's all predetermined anyway
4. present hedonist - towards pleasure, away from pain (separate from epicurean hedonist, possibly eastern thought: the middle way)
5. future goal oriented - work now, play later (puritan)
6. future afterlife - life after death and dream of that. (abrahamic religions, christian, muslim, jewish, etc)
From the eastern thought, there is only the present moment and from this, we create the past. The past is nothing more than memories. When we reinterpret the past, we essentially have a different past. Groundbreaking advances and personal forgiveness etc, is a dramatic reinterpretation of the past. Mostly because there's new information or we discover something we didn't know before. The future is unknown.
At any given moment, the present always creates the past or the future.
In the case that the present creates the past is how you deal with things that come up: conflict resolution. If something happens and you make a huge fuss over it, then you are creating hell. You record this in memory and thus your memory says that you lived in hell. But at the same time if you have a positive view of the moment, you create heaven. So, at any given moment, you can make heaven or hell out of it.
In the case that the present creates the future is also how you think about things. I'm always reminded of the quote by Henry Ford "Whether you think you can or you think you can't, you're right". This is essentially a self fulfilling prophecy, or interpolation. Given the premise of past events (our interpretation of our memories) we can formulate a prediction for the future. Almost everyone I meet make the error of calling this confidence. In reality, confidence has nothing to do with past success, but rather the acceptance of all future outcomes.
Aside from the relative description of what the present is, there is a BBC documentary with Brian Cox trying to discover what is the constituents of time itself. So far, time is found mathematically to be quantized. But since we experience life in a smooth flowing way, the bits are very small. Think of sand flowing. Sure you can pick out the individual grains, but it still has the virtue of flow. Similar to a movie, where there are individual frames, and yet, the motion on the screen is flowing.
In my estimation, now is just a cross section of our lives. There is some flexibility here in that we can employ our brains to create both our memory of the past and our prediction of our future. The present is where it all is. And it's important to us, because this is the form we live in the universe.