Calculating Time 1

Important Points to Remember

- The Earth Rotates from West to  East
- Places to the East see the sun first
- Imagine the sun at 1 end, that is at the East and the Earth at the West rotating on its axis

                                 

                

                                           

 Now visualize the lines of Longitude on the Earth. All places on the same line of longitude will see the sun at the same time during the day.

When calculating time, we start from 0 degree longitude which is Greenwich Meridian Time (G.M.T) or the Prime Meridian.

So places to the East of the 0 degree line will be ahead of time, therefore, you will add time.
Likewise, places to the West of the 0 degree line will be behind time, therefore you will minus time.

Example:

If it is 1pm at 0 degrees, East of the 0 degree line will be past 1pm. so it could be 2pm, 3pm, 4 pm etc. and West of the 0 degree line will be before 1pm, so it could be 12 midday, 11am, 10 am etc.

So now that we know where to add or minus time, how do we tell the exact time of a place?

Well, the earth completes a rotation of 360 degrees in 24 hours. To determine how many degrees is equivalent to 1 hour, we divide 360 degrees by 24 hours. That is
                                     360 degrees = 15 degrees
                                         24hrs

This means that 1 hour is equal to 15 degrees of longitude

Lines of Longitude are counted at 15 degree intervals. That means, for every line of longitude moving to the East of the 0 degree line of longitude, you add 1 hour.
Likewise, for every line of longitude moving to the West of the 0 degree line of longitude, you minus 1 hour.


Another important thing to note is that
1. every hour has 60 minutes
2. every hour is 15 degrees
3. Therefore 60 minutes divided by 15 degrees equals 4 minutes

Here it is   60 minutes = 4 minutes
                  15 degrees

Therefore 1 degree = 4 minutes