Understanding Time Zones | Geography for Year 6 PDF Download

Why are there time zones?

The Earth takes 24 hours to complete one full rotation on its axis, and to manage this, we divide the globe into 24 time zones using imaginary lines known as meridians. These lines extend from the North Pole to the South Pole, intersecting lines of latitude. Each time zone represents one hour of the day.

An important imaginary line called the Prime Meridian runs through Greenwich, a place in London, UK. This line, set at 0° longitude, divides the world into the eastern and western hemispheres.

• Time in countries east of the Prime Meridian is always ahead of the UK’s time.
• Time in countries west of the Prime Meridian is always behind the UK’s time.

The International Date Line (IDL), located approximately at 180° longitude (either east or west), marks the boundary between one calendar day and the next. It is positioned halfway around the globe from the Prime Meridian. When crossing the IDL:

• Traveling east, you subtract a day.
• Traveling west, you add a day.

Time in different parts of the world

As the Earth rotates, the Sun illuminates only the side facing it, resulting in:

• Daytime for regions where the Sun is shining.
• Night-time for regions on the opposite side, in the Earth’s shadow.

Time zones don’t always follow straight longitudinal lines; they often curve to accommodate country borders, as seen in global time zone maps. This division into 24 time zones—one for each hour of the day—helps coordinate time across the world.

Large countries like Australia or the USA span multiple time zones due to their size. However, smaller countries typically adopt a single time zone, even if parts of their territory cross meridian lines.