Week 10 - What time is it around the world? 

When one half of the world is in daylight, the other half is in darkness. If everywhere on Earth was the same time then it would mean that half of the world would be dark during the day and light at night, which would not be very useful to the people who live there. 

Please watch the video below which explains why we need to have time zones and how they work.

The history behind time zones: 

Many towns and cities around the world used to set clocks based on observing the sun and the stars. This occurred prior to the late 19th century. Dawn and dusk occur at different times at different places because of the Earth's rotation. Originally, the need for time zones arose in Britain when English sailors needed to know the longitude at sea. By dividing the world into several sections, or time zones, this was much more simple.  Time zones were created to give a uniform standard of time, but at the original time of the first internationally recognized time zone’s emergence, various countries had their own time zone standards. According to reports from Greenwich Mean Time’s website, before the coming of railways to Britain, there was no need for each city to keep in sync with another city’s exact time. For example, the city of Bristol had their own different local time than London did. Before GMT became regulated as the first time zone standard, some pre-1880 British clocks had two minute hands; one to display the local time and the other to display Greenwich Mean Time.

Today the whole of Britain is in the same time zone, however some countries are so large that they cover more than one timezone.

What are time zones?

The Earth is separated into lines of longitude (or segments) of 15 ^o each, starting at Greenwich, in England. Greenwich mean time is the time by which all the other times around the world are calculated. This line is 0 degrees longitude. The international date line is at 180 degrees longitude and is the line where one day ends and the next begins. Time zones were created to help people know what time is it now in another parts of the world. There are 24 separate segments or time zones because there are 24 hours in a day. Below is a map showing their boundaries. The time zones are not exactly straight lines because, where possible they go around the edges of countries, so that the time in that country is constant.

The international Date Line: This is a line of longitude at 180 degrees from the Greenwich meridian. It is the point where one day ends and the next begins. Please watch the video below which explains it in more detail.

Task: Using the clock function on your iPad you are going to work out the times in different countries if the UK time is 12 noon. Please print out the sheet below and complete it.