Measurement of Time

Welcome to class.

Ancient people like the Egyptians knew and understood that the position of the sun in the sky could help them tell what time of day it was. A sundial tells the time of day by the position of the sun in the sky. The dial makes a shadow and the surface has markings on it to tell you what hour it is in the day. In the morning the shadow points to the west as the sun rises in the east. The shadow gets shorter and shorter as it gets closer to midday. Then the shadow gets longer as the sun moves towards the west. It is about how people used the sun and shadows to tell the time of day in the past. People today can still use this method if they do not have a watch with them.

Time is a physical quantity that tells the duration in which an action takes place. It is special resource that cannot be saved for future use: once it is gone, it cannot be recovers. Time waits for no one: yesterday is history, today is a gift and tomorrow is a mystery.

The standard unit of time in metric system is second(s). Time is very important in the day to day activities because it tells us when to sleep, when to wake, when to prepare for school, etc.

A girl sleeping
A girl waking from sleep
pupils on break

Time varies from place to place; the time in London is different from the time in America. The time in Nigeria is different from the time is Canada. The rotation of the earth brings about these time differences.

The time difference between Nigeria and South Africa is 1 hour. South Africa is 1 hour: south Africa is 1hour ahead of Nigeria.

The time difference between Nigeria and Ghana is 1 hour: Ghana is 1 hour behind Nigeria.

The time difference between Nigeria and United States of America is 6 hours. America is 6 hours behind Nigeria.

The time difference between Nigeria and China is 7 hours. China is 7 hours ahead of Nigeria.

So, if the time in China is 6:15pm, then the time in Nigeria will be 11: 15am. If the time in Nigeria is 4: 30pm, then the time is America will be 11:301m.


The time can be measured using different modern measuring instruments such as wrist watch, stop watch, pendulum clock, wall clock, etc. these instruments say the same and exact time.

Wall clock

A clock can be analog or digital. On the analog clock, the long arm says the minutes while the shorter arm says the hour. The red thin arm says the seconds. So, a complete cycle of the second arm is equal to 1 minute (i.e a step shift of the longer arm). A complete cycle of the minute- arm will bring about a single shift of the hour-arm from the ones number to another (1 hour).

A Clock

On the digital clock, the numbers are separated by colon (i.e two dots); the first two numbers before the colon says the hour while the last two numbers after the colon tells the minutes.

Digital clock


The standard unit of time in metric system in second. The metric units of time are minutes, hours, day, week, month, and year. It should be noted that the units can be converted from one value to the other, such as below:

60 seconds            1 minutes (min)

60minutes             1hour(hr)

24 hours               1 day

7 days                   1 week

4 weeks                1 month

12 months             1 year

52 weeks               1 year

365 days               1 year

366 days               1 leap year


Very short durations are measured in seconds while a longer duration is expressed in hours, days, weeks, months, years etc.


  1. Time helps in planning events
  2. Time helps to remember past events
  3. Time helps to catch up appointments


  1. What is time?
  2. —————– is the standard unit of time in metric system (a) kg (b) g (c) s (d) m
  3. Mention two importance of time.
  4. The long arm of the wall clock indicates ————- while the shorter arm indicates —————
  5. 120 seconds = —————— mins (a) 2 (b) 5 (c) 4 (d) 1
  6. List any 4 instruments we use in the modern day to measure the time
  7. List three metric units of time


  1. Convert to digital time a) quarter past 12 b) quarter past 11 c) half past 9 d) quarter to 8 e) five past 2 f) 12 o’clock

We have come to the end of the class. If you have any question ask using the comment box. see you in the next class. 

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