One version of lucid dreaming is that during slow wave sleep we can freeze our imagination and our timeline such that when re-enter REM sleep or re-awake back in bed our timeline has fast-forwarded. For example the opposing eye movements during REM sleep might make it too difficult to be conscious in REM sleep seeing as I never felt my eyes darting too fast in a lucid dream where many lucid dreams might occur in slow-wave sleep. There are repeating stages of slow-wave sleep after each REM period such that we're not immediately fast-forwarded to waking life. Under this interpretation waking life would be more of a recording than a dream because slow-wave sleep is too intermittent to be mapped into one waking day-long period. Then it'd be like REM sleep were physically bracing us for our next time-freezing period in slow-wave sleep where the the unconsciousness of REM sleep would accelerate us faster through time.
"In the tale, Oisín (a human hero) and Niamh (a woman of the Otherworld) fall in love. She brings him to Tír na nÓg on a magical horse that can travel over water. After spending what seems to be three years there, Oisín becomes homesick and wants to return to Ireland. Niamh reluctantly lets him return on the magical horse, but warns him never to touch the ground. When he returns, he finds that 300 years have passed in Ireland. Oisín falls from the horse. He instantly becomes elderly, as the years catch up with him, and he quickly dies of old age."