What is the International date line

Which is the International Date Line?

International Date Line (IDL) is an imaginary line on the earth's surface that defines the boundary between one day and the next. The International Date Line. Therefore, the term'International Date Line' is indeed a misnomer. It has never been laid down in an international treaty, law or agreement. This international dateline crosses the Pacific.

Internacional date line map and explanation

On the 180º length in the centre of the Pacific Ocean, the International Date Line is the fictive line that divides two successive calendars. This is not a completely flat line and has been shifted slightly over the years to meet the needs (or wishes) of the various Pacific Ocean states.

Notice how it curves to extend all of Kiribati, Samoa, Tonga and Tokelau into the Eastern Hemisphere. Just to the lefthand side of the International Date Line, the date is always one of the days before the date (or day) immediately to the right of the International Date Line in the western hemisphere.

In the times and dates shown below, please be aware that Tonga and American Samoa have the same period, but are one date apart, as American Samoa is located in the western hemisphere, on the opposite side of the Tonga International Date Line. If you continue your journey to the western part, please bear in mind that the journey in Fiji is one hours sooner than in Tonga.

You' ll also find that Hawaii, further eastwards from American Samoa, lies an  hour later. So if you drive eastwards across the International Date Line, one or 24 hrs will be deducted. The westbound crossing of the International Date Line leads to the addition of one tag. This global co-ordinated world clock system, formerly known as GMT (Greenwich Mean Time), is now shortened to ULT (Coordinated General Time).

Normally, this is the default timezone on which all other global timezones are located. Never observing summer times.

date line

The International Date Line, also known as the Date Line, is an fictive line that stretches between the North and South Poles and randomly separates each date from the next. Most of its length is 180 degrees long, but it diverges eastwards through the Bering Strait to prevent the division of Siberia and then diverges westwards to involve the Aleuts with Alaska.

A further eastbound divergence from the equator allows certain archipelagos to have the same date as New Zealand. This International Date Line is a result of the global use of timing instruments that have been designed so that the midday is approximately the same as the solar crossing the latitude (see standard time).

If a traveller, with a watch that he moved forward or backward by one hours when entering a new timezone, and a calender that he moved forward by one night when his watch indicated the middle of the night, returned to his point of departure, would find that, according to his own personal experiences, the date differed by one of the days from that of the people who had been there.

International Date Line offers a default means to make the necessary adjustments: travellers travelling east across the line postpone their calendar for one date, and those travelling west require their calendar for one second.

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