A longitude is an angle from the prime merdian, measured to the east (longitudes to the west are negative). Latitudes measure an angle up from the equator (latitudes to the south are negative). Figure 1. With an angle of longitude and an angle of latitude, we can locate any point on the surface of the earth.

Latitude is the measurement of distance north or south of the Equator. It is measured with 180 imaginary lines that form circles around the Earth east-west, parallel to the Equator. These lines are known as parallels.

LONGITUDE Lines of longitude run north-south, but provide east-west locational reference. Lines of longitude are called “meridians.” No two meridians are parallel to each other. Rather, all lines of longitude meet at both the North and South Poles, but are separated in between by varying distances.

equator

The five major parallels of latitudes from north to south are called: Arctic Circle, Tropic of Cancer, Equator, Tropic of Capricorn, and the Antarctic Circle.

Prime Meridian

prime meridian

Any circle drawn around the Earth divides it into two equal halves called hemispheres. There are generally considered to be four hemispheres: Northern, Southern, Eastern, and Western.

Null Island is an imaginary island located at 0°N 0°E (hence “Null”) in the South Atlantic Ocean. This point is where the Equator meets the Prime Meridian.

The International Date Line, established in 1884, passes through the mid-Pacific Ocean and roughly follows a 180 degrees longitude north-south line on the Earth. It is located halfway round the world from the prime meridian—the zero degrees longitude established in Greenwich, England, in 1852.

The 180th meridian or antimeridian is the meridian 180° both east and west of the Prime Meridian, with which it forms a great circle dividing the earth into the Western and Eastern Hemispheres. It is common to both east longitude and west longitude.

Greenwich

In order to avoid the confusion of having different dates in the same country, the International Date Line bends and goes zig zag at the Bering Strait between Siberia and Alaska, Fiji, Tonga and in some other islands. …

The International Date Line (IDL) passes through the Pacific Ocean. It is an imaginary line, like longitudes and latitudes. The time difference on either side of this line is 24 hours. So, the date changes as soon as one crosses this line.

The dateline runs from the North Pole to the South Pole and marks the divide between the Western and Eastern Hemisphere. It is not straight but zigzags to avoid political and country borders and to not cut some countries in half.

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. This adds up to a difference of 24 hours or one day between east and west of 180 degree line of longitude.

When you cross the IDL, the day and date change. If you cross it traveling westward, the day goes forward by one, and the date increases by one. If you cross it traveling eastward, the opposite occurs.

Kiribati

Gisborne, North Island New Zealand is the closest city to the International Dateline, and so you sees the sunrise before any other city in the world.

Francis Bret Harte

Close-up of world map (from my office) showing the International Date Line in red. Samoa (and American Samoa) are just to the right of the line, New Zealand is in the bottom left corner, and Hawaii is at the top. The first thing to note is that the International Date Line is not set by international law or any treaty.

No, the time in Hawaii is UTC – 10 hours, and the time in Japan is UTC + 9 hours. So Japan is 19 hours ahead of Hawaii. If they were on the same side of the International Date Line, Hawaii would be five hours ahead of Japan. No, they are not.

Guam claims to be where “America’s Day Begins,” but that’s not technically true. Fifteen-hundred miles further east, right next to the International Date Line, there’s a tiny speck of land — a military base, where the sign on the airstrip once read “Where America’s Day REALLY begins.”

island of Taveuni

The prime meridian separates the eastern hemisphere from the western hemisphere. Halfway around the world, at 180 degrees longitude, is the International Date Line. The prime meridian is the line of 0 longitude, the starting point for measuring distance both east and west around the Earth.

World Time Zones

UTC+11 is a time offset that adds 11 hours to Coordinated Universal Time (UTC). It is observed in the BST, KOST, MAGT, MIST, NCT, NFT, PONT, SAKT, SBT, SRET, VUT during standard time, and in the AEDT, LHDT during the other months (Daylight saving time).