a scripture in Ezekiel says that 'one day is as a thousand years and 1,000 years is as 1 day'
if you are on earth, a day is seen as the sun moving through the sky, it rises in the east and sets in the west...and that is 1 day.
but if you were watching from out in space, you wouldnt see the sun moving around the planet... you would see the planet slowly spin on its axis ... big difference.