International Date Line – Must know for seafarers!

International Date Line – Must know for seafarers !

Table of Contents

What is International Date Line (IDL)? 

International Date Line is a jagged line drawn on the map of the central Pacific Ocean, near, and in many places coincident with, the 180th meridian extending between the North pole and the South pole.

It is located halfway around the world from the prime meridian, the 0 degrees longitude line.

The International Date Line curves eastward across Siberia, westward around the Aleutian Islands, and eastward around Fiji and New Zealand to avoid crossing land.

It is the point on a transpacific journey where navigators modify their date by one day. East of the line, it is one day sooner than west.


When was International Date Line established?

The international date line was established in 1884 by the International Meridian Conference. 

The conference was attended by 26 countries, and they chose 180 degrees longitude because it runs over an open ocean (the mid-Pacific Ocean), and they altered (zagged) it to keep the surrounding nations, particularly island ones, on the same day and date.

Why is the International Date Line in the middle of the Pacific Ocean? Why do navigators change the date by one day when crossing the international date line?

IDL is in the middle of the Pacific Ocean close to the 180-degree meridian because of the virtual absence of land and civilization in the region.

The navigators (both Nautical and Aero) going westward add a day to their calendars (for example, the day after October 5 would be October 7) and navigators (both Nautical and Aero) going eastward subtract a day from their calendars (for example, the day after October 5 would be October 5) to correct for this gain or loss.

Because the traveller is following the apparent motion of the sun, any traveller circling the globe in a westward direction lengthens the day by one hour for every 15° of longitude travelled.

By the time he or she has travelled completely around the world, the traveller is one full day ahead of the people who remained at the starting point of the trip. Similarly, travelling eastward leaves one day behind.

What will happen if International Date Line is a straight-line coinciding with 180 meridian?

IDL is not straight and deviates from the 180° meridian at many points. In some places, it appears as a zigzag, line deviating to the meridian’s east or west.

Because of the variances, places with similar economic and political ties can share the same date or time. If the International Date Line were a straight line, it would have divided some landmasses into two portions on the same day, with two distinct dates.

What is a line crossing ceremony?

Long-held traditions in navies (both military and merchant) and other maritime services around the world include ceremonies aboard ships to commemorate a sailor’s first crossing of the Equator, as well as crossing the International Date Line.

Since the olden days, this entire ceremony is held to pacify King Neptune (the ruler of the sea) by showing him respect, thereby keeping a sailor away from the perils of the sea and bringing him good luck. 

The main idea of the ceremony is to have fun and make the moment memorable, as crossing IDL or equator is considered a milestone in a sailor’s life. 

Usually, the Captain is made to dress up as King Neptune with a crown on his head, holding a Trident sceptre & beside him one of the crew members is dressed up as his wife, Queen Amphitrite. They both are surrounded by some more sailors to give a royal proceeding look.

The first-timers (called Pollywogs) are asked to remove their clothes to a bare minimum & are dipped in water in a big tub or hosed down. 

Mostly all those who cross for the first time (mainly the juniors or the trainees) have their heads shaved off, their bodies are painted in various types of paints and raw eggs are cracked over their heads. 

They all are made to drink a blended drink mixture of beer, raw eggs, some sauces etc. By drinking this mixture, the pollywogs swear to always speak the truth & offer loyalty to King Neptune. 

Depending on the weather condition a procession is carried out on the main deck with all shipmates dancing and singing. 

Later the certificate is issued by King Neptune (Captain) with a seal to all those first-timers who participated in the ceremony of crossing the International Date Line or equator.


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