Time Zones Explained
Why Are There Time Zones?
Though the Sun appears to rotate around us each day, we are in fact rotating about our own planet's axis, and we spin in and out of the Sun's light every twenty-four hours. Because we can't all have sunlight at the same time, our days are staggered, so when it's morning in one country it's evening in another.
Time zones are a tricky concept to grasp, but once you get your head around how they work, you'll always know what time it is, wherever you are. It's easier than going away and trying to memorize how many hours ahead or behind they are back home.
The planet is divided into 360°, or imaginary lines which run vertically from pole to pole. These lines are called Meridians. The Prime Meridian, at 0°, passes through Greenwich, England. Time zones are determined by how many degrees east or west of the Prime Meridian one is, up to 180°, which is on the opposite side of the planet, and the location of the International Date Line. This is where time changes a whole day.
How to Use Them
To figure out what time zone you are in, you'll either need a good memory or a world map. If you're using a map, you can look at the lines of longitude to determine the different zones. The world is divided into twenty-four different time zones; twelve east and twelve west of the Prime Meridian. Each zone is 15° of longitude wide.
Once you are looking at the Prime Meridian on your world map, count the number of 15° sections until you reach your location.Then take the time at the Prime Meridian and add if you are west of it (eg. Canada) or subtract if you're east (eg. Russia). The number of time zones is equal to the number of hours to add or subtract to the co-ordinated universal time (UTC), at the Prime Meridian.
For example, if you are in Toronto, Ontario you are six time zones west of the Prime Meridian; or six hours less than UTC. If it is 12:00 noon in Greenwich, England, then it is 6:00 am in Toronto. This is standard time, not daylight savings.
If you're not using a map, you can memorize the different time zones and apply it to wherever you are.
Sources: Navigation Training for Aviation; From The Ground Up.