Time is a consequence of change. Time is a construct of the mind. Time is an experience, a way to extrapolate and sort out causal events in the spacetime continuum. When we observe the movement of a watch, the ageing of our bodies, or the sun rising or setting on the horizon, we become comfortable with the notion of time. We may automatically attribute a change in states to the force of time. Yet, time does not cause our watch to tick, alter our bodies, or propel celestial objects through space.
Time is relative. With regards to the subjective realm, perception of time does indeed depend on our state of consciousness. In a state of flow or transcendence, where our minds are deeply immersed in the moment, the sense of time becomes less prevalent. What remains is a sense of space where sensory perceptions, thoughts and emotions flow effortlessly through the mind. Everything is perceived to be happening in an infinite space called now, a moment not bound by the perceived constraints of time.
In deep sleep, a coma or even death, time has no subjective relevance. There is no observer and no observation. This brings up an interesting philosophical question: if there are no observers in the universe, is there a universe at all? Similarly, if a tree breaks in a forest and no one is there to hear it, does it still make a sound? A possible answer may be the following: when the tree breaks, it does generate pressure waves in the air. However, as long as there is no one to interpret the waves, it does not make any sound. Sound is the conscious interpretation of the waves moving through space. Without a conscious observer present, the pressure waves remain only as potential sound. In the same way, a universe without an observer means there is no experience of a universe, yet that does not negate its existence.
Ultimately, the past, present and the future is happening in the now. The past happened now, the present is happening now, and the future will happen now. When we reflect on the future, we project a thought about the future, now. The future is an illusion in the sense that nothing can ever occur in the future. That is because now is not defined by time in a linear sense. Rather, now is the spacetime in which all things occur. We are, like all matter in the universe, bound by the laws of nature, so we evolve as everything else does "in time". So, unfortunately, we cannot observe the beginning and the end of the universe as individual human beings in one instant. But from the perspective of the universe itself, time is irrelevant.