Henry’s Resources We should already know (or at least remember) that the first effect that ROTATION has on the Earth is DAY & NIGHT. The second effect is it allows us to be able to calculate time But how does it do that? You ask!!! Ok First thing , as always ….let us use what we know ….to figure out what we don’t know… The Earth makes one complete rotation in 24 hours or 1 day. One complete rotation looks like this right??? Therefore we can say that 24 hours is the same as 360 degrees; If we write it as an equation then it would look like this …right? From knowing this we are able to calculate time. The Earth can then be divided into a number of time zones. Every fifteen degrees we then either gain an hour or lose an hour. The Sun rises in the ______________ and sets in the _____________. Therefore it would make sense to think those people in the East of the Earth would see the sun first and hence their day would have started first ….while those in the West would be a little behind in time. With this reasoning The RULE is made that time is advanced going East and lost going West. In other words