Why does the international date line seem to wiggle back and forth?

Answer 1

Ideally, the line should follow the meridian of 180° longitude. The purpose of the

zigs and zags is to avoid splitting a state, a country, or an island into two different

calendar dates. Imagine living on a small South Pacific island where this side of the

island and that side had two different dates. The state of Alaska would also be in

that same predicament if the Date Line followed the 180° meridian.

Answer 2

When the world became populated enough to actually worry about then the time actually was, people had already settled enough towns and villages to have to worry about which town would go where in the time zone. I know that sounds wierd, but it's like this. In one state, there would be two towns like ten minutes of each other, right? Like St. Paul and Minneapolis in Minnesota. When they were first settled they were far apart, but as they grew they grew together. Well lots of places were like that, and because some places were going on the same time that weren't in the same line exactly, they zig-zagged the line to make an exception. There's other places where the time zone splits the town exactly in half. Try living in a place like that! But when the time zones were drawn in the 1800's, they tried to make it as easy as possible for the major and minor towns to pretty much keep in the same time zone.

Answer 3

For the convenience of people living near the meridian that would otherwise be the boundary. The boundaries are generally adjusted to follow political boundaries e.g., state lines, so that people in a state are all in the same zone.

Answer 4

That was done intentionally, in order to avoid splitting any single nation, island

group, island, state, city, county, town, or village into two different calendar dates.

Alaska would have been one of them if the IDL had simply followed the meridian

of 180 degrees longitude.

Can you imagine what life would be like if you phoned up the doctor's office for

an appointment and they told you to be there at 11:30 on the 14th, but you

weren't sure whether the doctor's office was on the same date as your house

or on the next day ? !

Answer 5

When the IDL was designed and defined, a number of zigs and zags were built

into it, in order to avoid splitting any single state, country, or island group into

two different calendar dates.

If it had simply followed the meridian of 180° longitude between the poles, then

there would have been several places on land where walking, or driving your car,

a mile east or west would have changed your date to a day earlier or later.

Incidentally, one of those places is the state of Alaska, where the Aleutian chain

of islands crosses the meridian of 180° longitude. That puts a part of the USA,

and a part of North America, in the eastern hemisphere, and if the IDL had been

built without a wiggle in the right place, it would have put a part of the USA

forever in yesterday.

Answer 6

In order to avoid crossing any single city, state, nation, or island group.

If that were not done, there would be states or islands that had two

different calendar dates in different places ... you can probably imagine

what confusion that could lead to.

The state of Alaska crosses the meridian of 180-degrees longitude, so

it's one of the places that's spared that fate.

Answer 7

So Islands that are geographically close together or are part of the same Country can share the same time zone and so that time won't get messed up.

Answer 8

It is up to individual countries to decide their timezones and hence which side of the Date Line they are.

Answer 9

Because they have been moved back and forth for convenience (e.g. so 2 adjacent large cities on different sides of original time zone boundary can be in same time zone).