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Do You Know Why International Date Line is not straight?

22-FEB-2018 18:25

    As we know that the earth’s shape is spheroid, but do we know that how to determine time, date and locate places on earth. For that matter, we have to draw some imaginary lines like longitude, latitude, equator, prime meridian for navigation and geographical information.

    In this video, we will discuss about why International Date Line is not straight,

    But before moving on we must know that

    How places are located on the globe?

    North Pole and South Pole are two reference points on the Earth and with these two points, a line is drawn which lies exactly midway between the poles i.e. called Equator.

    Poles and Equator

    Further, we drawn a network of lines i.e. lines of longitude and lines of latitudeto locate places accurately. These lines intersect each other at right angles and create a network called a grid or graticule. These graticule helps us to locate places on the surface of the Earth accurately.

    Geographical Graticule

    Source: http: desktop.arcgis.com

    Now let’s see,

    How to determine time and date of that place?

    The Earth takes 24 hours to rotate through 360 degree (longitude). Hence, two places that are 15 degree of longitude apart have a difference of one hour.



    As the Sun rises in the east and sets in the west. This adds up to a difference of 24 hours or one day between east and west of 180 degree line of longitude.

    In other words, if a traveller crossing the date line from east to west, he/she loses a day and while crossing the date line from the west to east, he/she gains a day.

    But if it happens on same land mass, then same place would have different date in the same day. So, International Date Line has drawn to unite the world’s time-table and date to maintain uniformity across the globe.

    What is Cartography and how was the first map come to the modern World?

    Why International Date Line is not straight?

    It is International Date Line which is drawn at 180 degree longitude to determine the date which is passed through the Arctic Oceans, Bering Strait, Pacific Ocean, Antarctica, Fiji, Tonga and other islands.If we see this imaginary line, then we found, it is not straight but zig-zag line.

    International Date line

    Source: c.tadst.com

    But, if it is a straight line, then it demarcates the same land mass into two parts and then both places have different dates on the same day. It would be very inconvenient if one part of a country had one date of the week while another part would have the different date.


    International Date Line marks the place where each day officially begins. At the international date line, the west side of the line has been always one day ahead of the East side, no matter what time of day it is when the line crossed.

    Hope, you have understood that why International Date Line is not a straight line.


    What do AM & PM stands for?

    DISCLAIMER: JPL and its affiliates shall have no liability for any views, thoughts and comments expressed on this article.

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