How long is "now" ?

"How long is 'now'?"

It's an interesting question isn't it?

For me, it seems to be activity and location bound...

As long as I am participating in a certain activity and not changing locations (and the activity doesn't take too long, but then again, what is "too long" in this case?) I treat it as "now"...

Now, I know for many people this is quite different.

I am curious to hear your thoughts on this rather intricate subject.

Now would be something that I am currently doing. The duration may vary depending on the activity. It might have started a while ago and it might finish in a while.

*A*----B----C

A: I am currently playing
B: In 5 minutes, I will still be playing
C: I will finish playing in 10 minutes

A----*B*----C

A: I started playing 5 minutes ago
B: I am currently playing
C: I will finish playing in 5 minutes

A----B----*C*

A: I started playing 10 minutes ago
B: 5 minutes ago, I was still playing
C: I just finished playing

"A-B-C" were all the "past, present and the future" depending on how you see it.

I also think the length of "now" is dependent on the context used by the speakers, though I've encountered instances like:

Me: "Are you done with the text analysis? We have to turn that in next week"
Person A: "Not yet, I'm doing it now."

It could mean:
a. Person A is has been doing the thing at the moment, in which we can assume that he/she had started some time ago. But how long? Probably depends on the activity or how fast the person does it.
b. Person A is just about to start doing it, like saying "Now, let's start with our activity on yada yada yada yada" which means the guy is about to procrastinate and might be lying. In this case, 'now' is like a minute or a few minutes, or probably 'not existing'.

On the case of "Now, you know!", probably it starts from the time of realizing something and may continue on forever (unless it's a mistake and someone corrects you about it).