Did you know that the moon's distance from Earth varies each month? It has a rather eccentric orbit and it is moving away at about one and a half inches per year. Scientist attribute this to tidal friction with the Earth's oceans which also slows down how fast the Earth rotates, This lengthens the day by about 1 second every 40000 years. Okay, it is not something we really will notice or need to worry about, but because scientists can do simulations, they can figure out that four and a half billion years ago when the moon was being formed it was only about 15,000 miles from Earth, Back then an Earth day might have been only 5 or 6 hours long and there would be 1400 days in one year. More recently, at least relatively, around 900 million years ago there would be 480 days of about 18 hours each in one Earth year. THat would give us a very different life. Projecting into the future, we would expect longer days but fewer of them in a year.