Answer:
I am in the past never in the future. I don't exist but have existed. I saw what you saw and that is what I will ever see.
I can be repeated but rarely in the same way. I can't be changed but can be rewritten. I can be passed down but should not be forgotten.
Taken from a mine and then locked up in a wooden case. I am used by students everyday.
I am a mini solar powered computer.
Everyone in the world needs me. They generously give me but never take me. What am I?
What is always coming but never arrives?