What is timelessness?
It comes down to perception. How fast or how slow time appears to move, or not move, depends entirely upon your perception of it. Awareness shapes reality. But what shapes awareness? Like dreams, it may seem like a few hours have passed, but in actuality, or rather on the objective level of ordinary reality, perhaps only a few seconds have passed.
It is possible for a few seconds to feel like a few years, and for a few years to feel like a few seconds. An entire lifetime looked back in retrospect from the perspective of old age, viewed as a memory, may feel like seconds, like many years compressed into a few seconds, highly dense, concentrated, instant knowing, super fast data compression, that is memory, and without memory there would be no awareness of time.
Timelessness is the perception of stopping time, or of time moving very slowly, or perhaps so fast, that it appears to stand still.
What remains is the now, containing future and past, overlapping the present, not as separations in time, but one vast experience of potential energy, of what happened, what could happen and changes along the way, modifications of actuality, modifications of memory, modifications of perspective.
What has happened has happened. Can't undo anything, ever, just as the blowing of the wind, or lightning striking, cannot be undone, but you can change the way you see it, the way you remember it, what you look at, what aspects you focus on, what you consider important or unimportant; that is entirely changeable, alterable, maleable.
The experience of timelessness removes the boundaries separating the importance between yesterday and tomorrow. They are like wind currents and waves in the sea, changes of direction and velocity, like boundaries on the map; countries and capitals; points of reference useful for navigating the world in abstraction.
Memories are a lot like dreams; phantoms, yes it really happened but, after the fact, looking back, it's like a shadow. The reality of it has evaporated, has become as seemingly intangible as the wind.
We have time to measure our lives, to give us a sense of order and coherence, and a feeling of permanence and control, but ultimately the actual essential experience exists in a state of timelessness, real life lived in the now, what we experience in any given moment without regard to past or future.
You read this now. Ten minutes later. Tomorrow. Next year. Whenever. It doesn't matter. If you are here, whenever you are here, reading this, you have just transcended the barriers of time. Congratulations: you are a time traveller! Different times, different positions in space, and yet we are both perceiving it as happening now.