Hi everyone, my name is Blublubox. I come from the planet Blebeep, and I'm visiting the Earth. Sam has asked me to stay with his family for a few days, and I've discovered many interesting things while I've been there.

This week, they're celebrating something called "Christmas". Sam has aunties and uncles who live in England, America and Canada, and his family has phoned them to wish them all a "Merry Christmas". Something very strange has happened, however. They phoned them all at different times on different days. When they phoned England, it was night time here in Sydney, but their Aunty and Uncle were just getting out of bed on Christmas morning. Sam's family waited until the next day to phone the relatives in Canada and America. They phoned the relatives in America at 9 am. It was 4 pm on the day before there! Then they waited another two hours to phone the relatives in Canada. At 11 am in Sydney, it was 4 pm in Vancouver, still on the day before. Something very strange was going on. Sam explained to me that his relatives lived in different world time zones. I decided it was time to find out more.

Did you know that the Earth rotates on its axis? As the Earth spins, the Sun only shines on the part of the Earth that is facing it. It is night in the other parts of the Earth. The Earth rotates quite slowly (it takes a whole 24 hours for it to rotate once fully), so the Sun starts shining on different places at different times. We want midday (12 noon) to be the time when the Sun is at its highest point in the sky. This happens at different times in different places on the Earth, so the Earth has been divided up into different time zones. Some countries like Australia, the US, Canada and Russia have to be divided up into three, or even more time zones because they are so big. Most countries, like New Zealand, have only one time zone. The map below shows you the different time zones that the Earth is divided up into.

Sam told me about something else that was strange. In many parts of Australia and New Zealand, people deliberately change their clocks by an hour at certain times of the year. The reason for this is so that people can get more done during the hours while the sun is shining in the Summer. They set their clocks forward by one hour for the Summer, and then set them back by one hour (to the real time) for the Winter. Computers and mobile phones automatically adjust their clocks to the new time. Other clocks have to be set by hand.