The earth is approximately spherical(better called a spheroid) an on the surface of the Earth lies imaginary vertical and horizontal lines which can be used to calculate or determine the day and time of any geographical location using another location as a reference point.  This imaginary lines or points are of intense use in Geography and collectively known as Geographic coordinate system
<h2>Latitude And Longitude</h2>Latitude is a geographic angular distance ranging from 0° at the equator to 90° to the north or south pole. The angular distance to South is negative(-90°)while the angular distance to the North is positive(+90°). Lines of latitude runs horizontal varying diameter and in parallel to the equator. Abbreviations for latitude include Lat and φ. The north-most circle of latitude 23.4°<sub>[ref](https://en.wikipedia.org/wiki/Nigeria)</sub> on earth is referred to as tropic of cancer  or Northern tropic and on it, the sun  appears directly overhead.
<div class="pull-center"><img src="https://s6.postimg.cc/k6780aik1/longitude_latitude.png"><center><br><sub>Image credits:<a href="https://creativecommons.org/">Creative Commons Universal Public Domain</a> Wikimedia, <a href="https://commons.wikimedia.org/wiki/File:Latitude_and_Longitude_of_the_Earth.svg">Link</a>]</sub></center></div>

The equator which has a latitude of 0° and also the imaginary center of the planet is a line that divides the planet into Northern and Southern hemisphere 

Longitude is an angular distance ranging from 0° at the equator to +180° eastwards or -180° westward. The lines of longitude runs vertically with varying curvature(diameter). The symbol for longitude is the Greek word lambda (λ).

Longitude and latitude are simultaneously used to give the precise location of anywhere on planet Earth. Assuming you have a handy world map and trace  latitudes 4° and 14°N, and longitudes 2° and 15°E.<sub>[ref](https://en.wikipedia.org/wiki/Nigeria)</sub>, you would see that this coordinates is the location of Nigeria. In such coordinate are all countries of the world described in terms of location for Geography students. This geographic coordinate is of intense importance for  Ocean navigators, mariners and explorers.
<h3>Time And Day Of The Earth</h3> *Time is vital to humans, a wise saying quotes that time is money and time lost or mismanaged cannot be recovered.*

<div class="pull-right"><img src="https://s6.postimg.cc/juud0twi9/clock.png"><center><br><sub>Image credits:<a href="https://creativecommons.org/">Creative Commons Universal Public Domain</a> Pixabay, <a href="https://pixabay.com/en/clock-time-hour-time-clock-minute-2939565/">Link</a>]</sub></center></div>
With knowledge of latitude, you can determine the time in any part of the earth using your present geographic location  or any other location as reference point. Though GMT(Greenwich Mean Time) the  time of countries located in 0° longitude is always used as reference or standard time in sports and even in smart phones.
Every 15° difference is 1hour using GMT(longitude 0°) as reference.  If it is 15°  Eastwards or Westwards it would be +1hour or -1hour respectively.  Subsequently, every 1<sup>o</sup> difference is +4minutes or -4minutes

<h3>Examples</h3> 
1. The time in Ghana with Longitude 0° is 8:00AM what would be the time in Nigeria with latitude of  14°N and longitude 15°E
<h5>Solution</h5>15°E = +1hour<br>
Time in Nigeria= Time in Ghana(Longitude 0°) + 1hour<br>
Time in Nigeria=8+1= 9<br>
Time in Nigeria= 9:00AM. So, Nigeria time is GMT+1
2. The time in London(Longitude 0°) is 12:00PM what would be the time in Atlanta with Longitude and latitude of  33° 74´ N, 84° 38´ W<sub>[ref](https://www.worldatlas.com/webimage/countrys/namerica/usstates/uslatlog.htm)</sub>
<h5>Solution</h5>15°W = -1hour<br>
84°/15° =5 remainder 9<br>
 =5hrs 36mins (recall any 1°W is -4minute)<br>
Time In Atlanta= Time in London - 5hrs 36mins<br>
 = 12hrs - 5hrs,36mins<br>
= 12:00-05:38<br>
= 6:22AM<br>
 the time in Atlanta is 6:22AM. So Atlanta time is GMT-5
<h6>Alternatively</h6>We can multiply the angular difference by 4 and later convert to hours
84*4 = 336mins<br>
336/60 =  -5hrs,36mins(Westward is negative)<br>
Time in Atlanta = Time in London - 5hrs 36mins = 12hrs - 5hrs,36mins<br>
= 12:00-05:38<br>
= 6:22AM<br>
3. The time in Nigeria with coordinates 14°N and longitude 15°E is 6:25PM what would be the time in Washington DC with coordinates 38° 89´ N, 77° 03´ W<sub>[ref](https://www.worldatlas.com/webimage/countrys/namerica/usstates/uslatlog.htm)</sub>
<h5>Solution</h5> The latitudinal difference of Nigeria and Washington DC=15°W +77°W(we have to move 15°W to get to the equator and then 77°W to get to Washington DC)
15°W + 77°W = 92°W<br>
15°W difference = -1hour<br>
To get the total difference in hours, we divide 92° with 15°<br>
92°/15° = 6hrs remaining 2°(recall 1°W = -4mins)<br>
92°/15° = 6hrs, 8mins<br>
So, time in Washington DC = Time in Nigeria-6hrs, 4mins<br>
= 6:25PM - 6hrs,4mins<br>
=00:21mins which is 12:21PM<br>
So Washington Time is Nigeria time -6 which is GMT-5
4. The time in Ghana with coordinates of 0° longitude is 5:00PM, a man in another country on the same latitude with Ghana checked his watch and discovered the time is 10:30PM, what is the longitude of that man's location.
<h5>Solution</h5>15°W = -1hour difference<br>
15°E = +1hour difference<br>
The time difference between the man's country and Ghana = 10:30PM - 5:00PM<br>
= +5hrs,30mins <br>
=330mins (60mins makes 1hr)<br>
=330/4 (recall that every 1° is 4mins difference)<br> 
=82.5° E

<h3>Conclusion</h3>Though the time in a location  0° longitude which passes  through Greenwich a place  in close proximity with London is used as reference or standard time(GMT) in calculating the time of countries located in different coordinates, you can still use any location as a reference point to calculate the time of any country provided you know its geographic coordinates which can be seen in world maps. 
You can set some questions for yourself and project your intelligence to a higher level.

**Thanks for your ample time, I remain your brethren** @ikchris
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<h4>References</h4> To know more about longitude and latitude in relation with human time, read more on the links below:
* [Geographic coordinate system](https://en.wikipedia.org/wiki/Geographic_coordinate_system)
* [Tropic of cancer](https://en.wikipedia.org/wiki/Tropic_of_Cancer)
* [Latitude](https://www.caliper.com/glossary/what-is-latitude.htm)
* [Time difference between two countries](https://timesofindia.indiatimes.com/How-is-the-time-difference-between-two-countries-calculated/articleshow/4872443.cms)
* [Greenwich Mean Time](https://en.wikipedia.org/wiki/Greenwich_Mean_Time)
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