We pass through three states of consciousness daily: waking, dream, and deep sleep. How do we experience time in these states?
We have five windows through which to experience the external world in the waking state: ears, skin, eyes, tongue, and nose. These sense organs are ever ready to come into contact with their respective sense objects. We gain perceptual experiences from these contacts that leave lasting impressions in our mind.
The evanescence of the external world brings out vividly the hand of time. Months and seasons continually change. Where there was once a body of water now there is a mountain. Where a famous edifice once proudly stood, there is a deep lake with the building submerged in its waters. On the personal level, comparing photographs taken of us in babyhood, youth, middle age, and so on we are impressed by the changes time has wrought on our body over the years. But interestingly, our "I" has always remained the same.
In the waking state our thinking, feeling, and willing influence our actions and determine the direction of our life. When we have nothing worthwhile to do, we feel bored. When we have to do something very unpleasant and not in tune with our nature, time hangs heavy for us and the miserable experience seems to last forever. On the contrary, when we do something we like, literally time flies.
Again, time slips away from us when we allow the mind to drift. Suppose we sit and brood at 8 am, deciding what to do next: have breakfast, watch TV, read the newspaper, take a shower, or what? After some thirty minutes we realize that we have been wasting time. The mind has taken us for a ride, making us idle away those thirty minutes. If only we had managed our time well with a planned daily routine, the mind would not have had a chance to hoodwink us into doing nothing but think about what we could be doing.
According to Vedanta, dreams are caused by impressions accumulated in our mind in the waking state, not only in this life but also in earlier lives. Dream thoughts and actions do not leave impressions in the mind. Reactions to them in the waking state, however, will. The notion of time-and space-we have in the dream state is different from that in the waking state. We cover unbelievable distances and traverse years into the past and future in a dream that lasts maybe for a few minutes according to our reckoning in the waking state. But the "I" that has dream experiences is the very same "I" that has waking experiences.
The body and the mind are both inactive in deep sleep, and the world does not exist for the person who is sleeping. In the absence of any object to experience, his "I" also is apparently non-existent. When he awakes from deep sleep, he describes his sleep experience as "I slept happily and did not know anything then." Being detached from our body and mind in deep sleep, we escape the miseries arising out of them: physical pain, stress, tension-to name a few. Time does not exist in deep sleep. On waking up, we remember who we are and go about our daily activities. That raises an important question: is there any continuity at all from the time we pass into deep sleep until the time we wake up?