Is there a way to prove that the past or future exists?

The idea of Proof requires verification from a person's physical senses...it's the way traditional science works. Even supposedly-independent results from a physical instrument require a human being to observe them and interpret them. (See Schrödinger's cat)

Most, if not all, humans already agree that the future doesn't exist (yet) because that's the nature of our linear-time illusion...the quantum waveforms of the future potential paths that exist from this moment haven't yet collapsed into a definite "real" physically-observable one until you give your conscious focus to one.

So your question is really about whether you can prove that the past is absolute i.e. exists outside of human perception.

Coming back to the first paragraph of this answer, how can you ever know if the past exists because you can only interpret the idea of the past through your physical senses i.e the past could completely alter at any moment and every physical measurement consistent with that alteration could also change and you would never know.

And, just to make it even more difficult, your so-called "memories" of the past are happening Now anyway :)

There is an insightful episode of the Sci-Fi TV series "Star Trek - The Next Generation" called "Yesterday's Enterprise" which illustrates these ideas pretty well. It's worth watching the full episode to give yourself a mind-bending workout :)

A snippet is here...

https://www.youtube.com/watch?v=52KFUdU1jaQ

I think the way the writers of the episode expressed the ideas of the participants being unaware they were suddenly living a different reality is pretty much the way it works for us in our non-Star-Trek lives :) (Of course, for the sake of engaging our perspective as viewers of that episode, they had to include one character for us to identify with that was able to perceive the temporal change)

Our "pasts" could well be in a state of constant flux but, being constrained by our physical senses, we wouldn't even know the changes are happening. And the changes would be entirely consistent with our newly-formed memories of the past.

So, to answer your question, No, I do not believe you could ever empirically prove the existence of the past...not from a human-based linear-time perspective anyway.

if your proof has to be that
of orthodox science, 3D,
the answer has to be no

is there existence outside
of 3D as new science
of creation, it is yes

Indeed, what is "proof". How can someone find proofs of a dream? Does it matter?

Here, I'll juts throw out random ideas as to why I believe yes, there sure are ways which may help you to agree.

To me, proving something means convincing my weak brain logic that whatever I sense out of reality will also be sensed by other people. Because, to me, life is about community.

What about someone who don't care about others, how could they verify they're not just fooling themselves? Why would they care to do so, anyway? I don't know. I think for our current biological state of "human" being, anything we can't connect with other beings don't really matter.

That being said...

"Proof" is indeed just finding consensus. The more people can agree, the strongest the proof.

In that sense, it's pretty much proven the past exists, and that it is unique. We can register it and verify later, it's really simple. As I write this, I'm committing my present into building a proof of past events.

As the future... Well...

We can predict some events in the future, pretty much like we can for some events in the past.

The universe as a whole is in constant motion. The Earth is rotating the Sun at staggering 30km/s - much much faster than a bullet, 10% the speed of light. With all that movement, it becomes complex and difficult to proof what was the state of a particular point in the universe in the far past. Sometimes even 1 second ago, but it's easier to picture this idea in Earth history, or the evolution of biological elements we can track here.

So the past becomes blurry depending on many things. Think about it.

To me, the only real difference between proving the past or the future is: we found out techniques, and we're probably "built" to, perceive just the past. In the other hand, our brain keeps making lots of calculations to predict many small events in the future, such as where our leg must fall down in order to prevent us to kiss the ground and walk. Something we couldn't make a robot do as efficiently yet, such complexity there is. But, nevertheless, that's a future certain to exist if we throw our leg upfront.

Some thoughts from my saved JKOnline Daily Quotes....

J. Krishnamurt

"To most of us life is action, and by action we mean something which has been done, is being done, or will be done. Without action you cannot live. Action does not mean only physical movement, going from here to there; there is also the action of thought, the action of an idea, the action of a feeling, of environment, of opinion, the action of ambition, of food and of psychological influences of which most of us are totally unaware. There are the actions of the conscious mind and the actions of the unconscious mind. There is also, is there not, the action of a seed in the earth, the action of a man who gets a job and sticks to it for the rest of his life; there is the action of the waves beating on the shore, the action of gentle weather, of rain; there is all the action of the earth and of the heavens. So action is something limitless. Action is a movement both within and out of time. I am thinking aloud with you; I am exploring. I came here with one thought, action, and I want to discuss it with you, go into it, explore it gently, slowly, quietly, so that you and I understand it together.But when you merely reduce action to: 'What am I to do? Should I do this and not do that? Is this right, or that?' then action becomes a very small thing. We do, naturally, have to act within time; I do have to stop at the end of the hour; one has to go to the office, the factory, take meals, at a certain time. There must be action in time, and that is all we know, is it not? You and I really do not know anything else except action which is recognizable and within the field of time. By time we mean yesterday, today, and tomorrow. Tomorrow is the infinite future, yesterday is the infinite past, and today is the present; and the conflict between the future and the past produces a thing which we call action. So we are always inquiring how to act within the field of time, of recognition. We are always asking what to do: whether to marry or not to marry, whether to yield to temptation or to resist, whether to try and become rich or seek God. Circumstances - which are really the same as time - force me to accept a job because I have a family and I have to earn, and so there is all the conflict, turmoil and toil. So my mind is caught in the field of action-within-time. That is all I know; and each action produces its own result, its own fruits, again within time. That is one step, is it not? To see that we are caught in the action of time." - Collected Works, Vol. XI",108, Action

When we are talking about time, we do not mean chronological time, time by the watch. That time exists, must exist. If you want to catch a bus, if you want to get to a train or meet an appointment tomorrow, you must have chronological time. But is there a tomorrow, psychologically, which is the time of the mind? Is there psychologically tomorrow, actually? Or is the tomorrow created by thought because thought sees the impossibility of change, directly, immediately, and invents this process of gradualness? I see for myself, as a human being, that it is terribly important to bring about a radical revolution in my way of life, thinking, feeling, and in my actions, and I say to myself, 'I'll take time over it; I'll be different tomorrow, or in a month's time.' That is the time we are talking about: the psychological structure of time, of tomorrow, or the future, and in that time we live. Time is the past, the present, and the future, not by the watch. I was, yesterday; yesterday operates through today and creates the future. That's a fairly simple thing. I had an experience a year ago that left an imprint on my mind, and the present I translate according to that experience, knowledge, tradition, conditioning, and I create the tomorrow. I'm caught in this circle. This is what we call living; this is what we call time.Thought, which is you, with all its memories, conditioning, ideas, hopes, despair, the utter loneliness of existence--all that is this time. ...And to understand a timeless state, when time has come to a stop, one must inquire whether the mind can be free totally of all experience, which is of time. - J. Krishnamurti, The Book of Life

peace