consciousness lets us know when "now" is

We need consciousness in order to remember the past and imagine the future. If we did not have a sense of the present (that we have when waking) we would not be able to know "when" we are. Memories would seem like hallucinations, as would imagined events. Maybe this is what goes on in dreaming. Maybe being conscious requires a huge amount of energy so the brain stops doing it at night to save energy (and we begin to hallucinate = dreams).