The International Date Line - If you want a group conversation that will lead to confusion just bring up the topic of the International Date Line (IDL) and see who understands it or who can explain it.
Q - Take a look at the image above - If it's 6.00 pm Sunday in Samoa what time is it in New Zealand?
In fact a better starter question is what day is it in New Zealand - is it Saturday, Sunday or Monday? Read on ....
If you cross over the IDL from east to west (Samoa to Fiji say) do you gain a day or lose a day?
New Zealand - Say 5 pm Monday afternoon in New Zealand.
London - New Zealand is 11 hours ahead of London GMT so it's 6 am on Monday morning in London (or Dublin).
New York - At that moment in New York (another 5 hours) it's just 1 am Monday morning
Los Angeles - It's another 3 hours earlier in Los Angeles means it is 10 pm on Sunday night there.
Samoa - it's another 4 hours earlier again in Samoa so that leaves the time there at 6 pm on Sunday night
So what this is telling us is that Samoa and other territories to the right of the IDL are treated as being in the American Time Zone and as we travel around the world from East to West (from New Zealand to Europe to the USA) the time gets earlier and earlier - across different time zones making up 23 hours in total. So, we see that at 5pm Monday in New Zealand it is 6pm Sunday in Samoa.
Therefore, in time zone terms crossing the IDL from East to West usually means jumping a day forward - in theory if the journey takes an hour you can leave Samoa at 6pm Sunday and it will be 6pm Monday when you get to your destination 1 hour later.
On the other hand if you leave New Zealand at 6pm on Monday and fly east in the direction of Samoa then 1 hour later it will be just 6pm on Sunday - you've gone back a day in time !!
Could you fly fast around the world and go backwards or forwards more than 1 day? Nope, as every time you do the circuit and cross the IDL the day you have gained (or lost depending on which direction you are travelling) resets.
And now that you know all this guess what? Samoa has just made a decision to move the IDL to the other side and from 29 Dec 2011 it will now be in New Zealand / Australia time and not US time. It is doing this for good economic reasons as NZ and Aussie are it's main trading partners. With the time as it currently is it means that when it's Friday in Samoa it's Saturday in NZ and when its Sunday in Samoa it's Monday in NZ - not ideal for regular weekday business trading.
Today 6pm Sunday in Samoa = 3 pm Monday in Sydney. After the change 3 pm Monday in Sydney = 6pm Monday in Samoa. At least the days of the week are lined up an that makes more sense if you live in Samoa !! But the change over itself will mean that Samoans will lose 1 full day in their calendar. Now, where did it go ???
