Fancy a date?

On some cruises, you cross the international dateline. Depending on which way you're travelling when you do this, you either gain or lose a day. If you've ever wondered why, this is my Physics-Degree-educated (a long time ago!) attempt at explaining this, and the concept of time-zones to you!:

We need a little bit of help from our old pal Mr Einstein and his Theory of Relativity here... You see, time is only relative to the place in which you are. The earth turns anticlockwise around its axis (if you take north as "up" anyway) which means somewhere to the East of where you are at any point in time will see the sun rise before you. This is because the sun doesn't really rise at all - the earth just revolves around so you can see it again.

It's a bit like a roundabout at a kiddies' playground - only one person can be looking in any direction at any time and depending on when it's your turn to be in the "right place" will depend on who sees what first. Time is just the same - but we have to have a starting point or everything would merge into one (a bit like Norway in winter!).

The place we choose for time to "start" is known as the International Dateline. It's a bit like 12 o'clock on a clockface - the morning starts there and the afternoon starts there. If we didn't have a starting point, we wouldn't have a morning or an afternoon. The reason we have days is because it takes a day for the earth to rotate completely once so the same point on earth can see the Sun in a direct line of sight. That's how we measure time... and a new day must dawn somewhere!

The International Dateline is really confusing for people that live near it - if you're on the east side of it, it's today and the other side of it is tomorrow, but on the west side of it, it's today and the other side of it is yesterday. Odd eh? Imagine living one side of town and working on the other... that's why it doesn't actually run through ANY countries - it's a sea-based line and it's imaginary so it doesn't really exist but it has to go somewhere!

So that we didn't all get horrendously confused, somebody at some point in time decided it'd be a good idea to make smaller deviations than just "today" and "tomorrow" so they divided the earth and its constituent nations up into 24 "time zones" within the circumference of the globe. In the UK, we're lucky guess - they use the line that passes directly through our country as the average time marker - hence "Greenwich Mean Time" - the line passes directly through Greenwich in London. Unlike the International Dateline, the line of Longitude that signifies where Greenwich Meantime applies is a perfect straight line running North to South - and it's pretty much diametrically on the opposite side of the globe to the International Dateline.

The United States of America on the other hand are such a big nation that they actually have 6 time zones just for themselves! How greedy!!! There are five time zones across the continental USA, then they add another for Hawaii, making a total of six:
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If it is noon in the Eastern time zone (Maine through to Michigan) then it is:
11 AM Central Time (North Dakota)
10 AM Mountain Time (Colorado)
9 AM Pacific Time (Oregon)
8 AM Alaskan Time
6 AM Hawaii Time
(Note the two hour difference between Alaska and Hawaii time.)

For fun, why not visit: http://www.worldtimezone.com/ to get a pictorial view of the time now, anywhere in the world.