But if you left on Friday at noon, you would reach the other island on Saturday morning at 9 AM. And if you walked back, it would somehow be Friday once more. You see, as Earth spins, sunlight reaches different places at different moments. So somewhere on Earth, today is always ending while tomorrow is already starting. So to keep everyone following the same calendar, a line was drawn across Earth, showing where the date changes to a brand new day. And these two islands stand on opposite sides o