Last reviewed: 25 October 2026
Latitude and longitude let us give the exact position of any place on Earth, and longitude explains why it is morning in Nairobi while it is still night in New York. These ideas appear regularly in junior school Social Studies. This guide explains both and walks through the time calculations that learners find tricky.
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Lines of Latitude
Lines of latitude are imaginary lines that run east to west around the Earth, parallel to each other. They measure how far north or south a place is from the Equator, which is 0°. Latitude goes up to 90° North at the North Pole and 90° South at the South Pole.
Important lines of latitude include:
- Equator (0°): divides the Earth into the Northern and Southern Hemispheres. It passes through Kenya, close to towns such as Nanyuki and Maseno.
- Tropic of Cancer (about 23½° N) and Tropic of Capricorn (about 23½° S).
- Arctic Circle (about 66½° N) and Antarctic Circle (about 66½° S).
Places near the Equator receive more direct sunlight through the year and so tend to be warmer, though altitude also matters. This is why Mount Kenya can have snow on its peaks despite being almost on the Equator.
Lines of Longitude
Lines of longitude, also called meridians, run from the North Pole to the South Pole. They measure how far east or west a place is from the Prime Meridian (0°), which passes through Greenwich in London. Longitude goes up to 180° East and 180° West. The 180° line is roughly where the International Date Line runs.
Giving the Position of a Place
A place’s position is given as latitude first, then longitude, for example roughly 1° S, 37° E for Nairobi. On a grid of these lines, find where the two lines cross. Remember to include the direction letters N, S, E or W, as a number on its own is incomplete.
Longitude and Time
The Earth rotates 360° in about 24 hours. So it turns 15° every hour (360 ÷ 24), or 1° every 4 minutes. Because the Earth rotates from west to east, places to the east see the sun first and are ahead in time.
The rule: going east, add time; going west, subtract time. A memory aid is “East Gains, West Loses”.
Worked Time Examples
- It is 12 noon at Greenwich (0°). What is the local time at 45° E? 45 ÷ 15 = 3 hours ahead, so 3.00 pm.
- It is 10.00 am at a place on 30° E. What is the time at 60° W? The difference is 30 + 60 = 90°, which is 6 hours. The second place is west, so subtract: 4.00 am.
- Two places are on 20° E and 50° E. The difference is 30°, which is 2 hours.
When both places are on the same side of the Prime Meridian, subtract their longitudes. When they are on opposite sides, add them.
Local Time and Standard Time
Calculations based purely on longitude give local time. In practice, countries use standard time zones so that a whole country or region shares one clock. Kenya uses East Africa Time, which is three hours ahead of Greenwich Mean Time (GMT+3), even though parts of Kenya lie at slightly different longitudes. Exam questions usually say whether to use longitude or standard time.
Common Mistakes
- Writing longitude before latitude.
- Forgetting N, S, E or W.
- Subtracting when going east.
- Adding longitudes when both places are on the same side.
Practise With a Globe or Atlas
Find five countries in an atlas, write their approximate positions, and calculate the time there when it is noon in Kenya. Our map reading guide covers scale and direction, and the Grade 9 Social Studies papers give exam practice. Use the exam countdown for free daily questions and the What to Revise report to target gaps. Full papers with answers are in the Monthly Pass (KSh 500 by M-Pesa).