There is a serious misconception about time. In reality, it does not exist at all. Einstein would probably agree.
Time is a mental conception confined to one's present perception. The past and future do not exist. No one experiences a time different from the current moment. One can remember the past. One can have expectations about a possible future event. To the extent these mental conceptions do in fact exist, it's only as a recollection or an imaginative fantasy about something which might happen.
Eternity simply means consciousness.
To doubt eternal life represents a bizarre delusional state of mind because one has never experienced anything other than eternity. Every second has no past or future. Every instant simply exists. Always has. Always will be. Eternity simply means no variation in one's normal state of consciousness.
Asleep, we dream. Even when unable to recollect these mental motion pictures complete with plots and subplots, a timeless state of consciousness occurred. We always awake later on. If we only dream during REM periods nothing is seriously refuted. Time existed only when conscious, and had no factual reality separate from the moment being perceived. For every reader, this moment is the only reality, not any prior or future event.
Everything in the universe moves. All 100 billion galaxies are in motion. So are the smallest particles inside a proton, neutron, or electron. Consequently, every thought moves on to the next, but there is never anything other than the present moment.
It is irrational to imagine the existence of any other condition - an event no one has ever experienced.
Even as a measurement, time itself exists only as a mental conception. A day is based on the rotational speed of the Earth. A year is its speed traveling around the Sun.
The present moment constitutes the only experience anyone has of these events. 40,000 years ago everything existing now existed in some form. 40,000 years from now all existing now will exist in some from.
The significant question is consciousness, not the relativity of time. Mankind worries a great deal about a condition no one has ever experienced. We always wake up. We even did that when we were born.