How long is present? When does present become past? Present exists as well it doesn't? How many seconds, miliseconds or whatever separates now from past?
A good introduction I found is The Experience and Perception of Time in SEP.
In terms of time, the "now" has a length of exactly 0. In terms of space, it has a length of infinity on each of its three axes.
The problem you are probably trying to address arises solely from our perception of time as well as the common usage of such terms in language. They are then defined subjectively through the individual as well as social norms.
There are two conditions that we can provide related to these:
- aware of something
- feeling of something
If we are aware of something, then we perceive differences. When we are feeling of something, we are not perceiving differences, but we are focusing on something.
For example, when we are thinking, we need to aware of something, we need to perceive differences to make a better comparison.
When we are drinking, there is less thinking activity here, there is mostly no perceive differences, but there is mostly focusing to feel what we drink. We need to perceive differences to keep something (for example, hold the glass), but mostly we do focus when drinking (to taste something).
Since perceiving slower time, fastest time and make a comparison, those are related to perceiving differences. Therefore our present are as long as we are focusing on something. The more we can focus on something, the more we stay within present. But once we perceive differences (we are not focusing on something), then our present become past and we experience new present as long as we can maintain our focus on something.