Normally, when people call something “timeless” is just means that it lasts a long time, but of course, it comes to an end and is not truly timeless because ,in the cosmic scheme of things, it is a passing phenomena.
Nothing, that is “no thing,” is timeless because things arise then change and disappear. That is the nature of the phenomenal world. There is another dimension, that of thethat is different. The meaning of this noumenal world is close to that of spirit, soul, essence, or archetype. It is the underlying reality that is behind, in and through all things. It is this reality, this spirit that is timeless where as all external things, all things physical, belong to the realm of time. The timeless realm, the archetypal realm, is the essence of all things. Out of this consciousness, Walt Whitman wrote:
“Nothing is ever really lost, or can be lost,
No birth, identity, form—no object of the world.
Nor life, nor force, nor any visible thing;
Appearance must not foil, nor shifted sphere confuse thy brain.
Ample are time and space—ample the fields of Nature.
The body, sluggish, aged, cold—the embers left from earlier fires,
The light in the eye grown dim, shall duly flame again;
The sun now low in the west rises for mornings and for noons continual;
To frozen clods ever the spring’s invisible law returns,
With grass and flowers and summer fruits and corn.”
Some other passages that convey something of the meaning of timelessness:
“The timeless in you is aware of life’s timelessness. And knows that yesterday is but today’s memory and tomorrow is today’s dream.”
― Kahlil Gibran, The Prophet
“That’s when I realized that certain moments go on forever. Even after they’re over they still go on, even after you’re dead and buried, those moments are lasting still, backward and forward, on into infinity. They are everything and everywhere all at once. They are the meaning.”
― Lauren Oliver, Before I Fall
“The wise realizing through meditation the timeless Self, beyond all perception, deep in the cave of the heart leave pleasure and pain far behind. The man who knows he is neither body nor mind, but the eternal Self, divine principle of existence, finds the source of all joy and lives in joy abiding.”
“Night after night on starry wings
Night lovers soared so high
Miles apart, across the oceans
Their love forgot to sigh
In heavenly flight’s timelessness
That highest height treasured
Into the deepest of all blues
Their depth of love measured.
From the poem ‘The Ballad of Night Lovers”
― Munia Khan, To Evince the Blue