Benjamin Schmidt
I am talking about the time of no experience. In a very practical sense: How does one know how much time has passed without experience? Looking at a clock? Using some other sensation as a proxy for a clock? 

This isn't really practically relevant for me right now. It's just a question that has come up a few times when talking with people about the concept.

I have read the chapter on fruitions in MtCToB and skimmed it again before asking the question, hopefully, I didn't miss the answer ;).

this stage typically lasts only an instant

There is a much smaller percentage of stream enterers who can get what is known as “duration”, meaning that they can have the Fruition last longer than an instant of “external time” (though after reality restarts and in retrospect, it seems to them like a timeless discontinuity with no passage of time at all, or other reference points for time or other experience), and those who can’t.

As an aside, for all my meditation abilities and by way of full disclosure, I am not one of those people who is certain that they have ever been able to stay in Fruition for some period that in external time was more than a fraction of a second.

And in another session it was significant.
My body become lighter , noting lightness , and nothing left to notice so i just notice "Knowing , Knowing"
and then suddenly "Snaps"
I only know it took about 20 minutes (i didn't know there was bell rang) after yogis are reporting already .

"Anuloma nana is the last nana in which there is anything happening. After that there is no awareness of anything. Feeling and awareness suddenly cease." [Sixteen Stages of Insight by Ajahn Jodok of Wat Mahathat]

"After the cessation, when awareness returns, the meditator contemplates what has happened to him. After this he goes on acknowledging the rising and falling movements, but they seem much clearer than normal. Considering what has happened is called paccavekkhana nana." [same source]

Benjamin Schmidt
Thanks, 
especially with the ones lasting only an instant, I was wondering how people notice that they had a time of no experience by noticing some change in external stimuli or whether they just notice the aftereffects of a cessation.
...

Enough Technical Stuff, What’s it Really Like?

The obvious question that most people have at this point is: what is it like? After all, it’s Nirvana – which is synonymous with “heaven” in the minds of many. There are a lot of confused ideas about what it is (or isn’t). My recommendation is to expect nothing – literally.

Practitioners who have experienced the moment of Nirvana struggle to put it into words, because describing it can make it seem anticlimactic even though it is truly extraordinary. What it feels like is that there is “click”, “blip”, or “pop” that occurs for an instant. When it first happens it is so quick that the meditator could even miss it. However most people do stop and ask themselves “what was that?” It can be a bit baffling because it seems like nothing happened, and that is exactly right. For an instant absolutely nothing happened. There were no shining lights or angels, no pearly gates or choruses of joy, no transcendent experiences of unity with the cosmos or the divine. It is nothing like that at all. It may not be until you really think about it that you realize what an extraordinary thing that instant of absolute nothing really is.

As you reflect on it you see that there was something truly amazing about that moment. In that instant everything disappeared, including you. It was a moment of complete non-occurrence, the absolute opposite of everything that has ever happened in your life up to this moment, because it could not really be said to have happened to you. No doubt, it is a weird realization, but there it is. Following the experience of this absolute nothing is what my teacher aptly calls a “bliss wave.” For some time following this moment of alighting upon Nirvana you feel really relaxed and fresh. These two experiences, seeing that you disappeared and that you also feel great because of it, lead to a very important discovery that will shape how you view yourself from this point forward. You begin to understand in a very deep way that there really is something to this whole idea that the cravings of a “self” are the root of suffering. When it was gone, even for an instant, life suddenly got much better.

For me, when this moment first happened it felt as if all of reality “blinked.” Another way I put it at the time was that “emptiness winked at me.” It’s a funny way to put it, but it actually felt that way. As if a shade was quickly drawn or an eyelid closed from the top of the field of awareness down to the bottom and then suddenly released. At first I thought it was a moment in which I just lost focus and the meditation fell apart. But the bliss wave hit a few moments later and I started giggling and laughing out loud. My wife was in the other room and I was trying not to sound crazy. I kept wondering if this was really it. For some reason I couldn’t believe it actually happened. In the hours following the blink-out I felt more ease and energy than I had in a long time. For example, I’m a morning person, not a night person (I go to bed embarrassingly early), but I stayed up almost all night and still felt amazing the next day. I walked around with a big grin on my face for quite some time after that. I just felt wonderful.

There is an important insight to be had regarding cessation, and it is worth pondering though no conclusions are readily available. During the moment of cessation you were utterly gone, and yet there was an awareness there to witness it happen. What does that mean? In Buddhism, as well as other contemplative traditions, the interpretation of this has been an issue of deep debate among the great mystics and masters. Whole lineages and traditions have clashed on differing understandings of this deepest dharma. Is emptiness really empty? Is everything awareness? There is no consensus as to what it means, or if finding a meaning even makes sense. Frankly, I am not fully comfortable with any of the explanations out there. What is important for you to know as the person on the cushion is that for an instant you were there, then you “went out”, and yet you have a memory of it happening. This implies something profound about existence that you will need to explore. Fortunately, you will not be the first one to be flummoxed by this paradox, and there are a variety of profound interpretations out there to support your integration of this experience.

Linda ”Polly Ester” Ö
If someone only notices that more time has passed than they thought, the most likely explanation is that they were dull or even asleep, or that they simply misjudged the time. To be sure that there is a cessation, one needs to have a clear door experience before the gap and a clear sense of coming back after the gap. You know that there was a cessation because you noticed going into it and coming out of it. If that happens and external stimuli indicate that one was gone for longer than an instant, then there is reason to suspect that maybe it was a cessation with duration. That has never happened to me. They have always been just an instant. 

When it first happens it is so quick that the meditator could even miss it.

All that said, there are those who won’t recognize it, particularly those who chance upon it outside of a meditative tradition that can recognize it. There will also be those for whom it happens within the context of their practice tradition, who can recognize it, but who fail to identify it as being what it is. Sometimes the afterglow is not so spectacular, though for most the series of insights, connections, syntheses, and the like that burgeon forth is impressive. Others will just go on practicing, not realizing what has just happened.

Often it is not possible to make a clear call about what was what, even if it was a Fruition.

> although we could probably have a long and crazy discussion about just what "nothingness" means

I am not aware of any psychological tests that might support this, but the mind becomes more sensitive and changeable with each level of enlightenment. It would seem that this is partly a result of being able to let go of a mind state more quickly. If you are able to let go of one mind state, then almost instantly another mind state will arise. If this ability is combined with the ability to consciously perceive processes which were previously unconscious, then the mind becomes more volatile.

My experience is that while time (and space) is constructed it is primarily marked by the experience of change.

But neither does time exist without change; for when the state of our own minds does not change at all, or we have not noticed its changing, we do not realize that time has elapsed, any more than those who are fabled to sleep among the heroes in Sardinia do when they are awakened; for they connect the earlier 'now' with the later and make them one, cutting out the interval because of their failure to notice it. So, just as, if the 'now' were not different but one and the same, there would not have been time, so too when its difference escapes our notice the interval does not seem to be time. If, then, the non-realization of the existence of time happens to us when we do not distinguish any change, but the soul seems to stay in one indivisible state, and when we perceive and distinguish we say time has elapsed, evidently time is not independent of movement and change. It is evident, then, that time is neither movement nor independent of movement.