The Concept of Measuring Time

This post explore the different methods of measuring time in different places and different points in history. We shall also take you through the use of timeline for measuring time intervals

• Time can be defined as the passing of one or any of the units mentioned above.
• Time can also refer to the past (time that is gone)
• The concept of time is measured using seconds, minutes, hours, days, weeks, months, years, decades, generations, centuries and millennium

Explanation of timings

•Decade:  a period of 10 years

•Generation:  a period of 30 years

•Jubilee:  a period of 50 years

•Century:  a period of 100 years

•Millennium:  a period of 1000 years

Date: This is the statement or period of time when something happened or when something used to happen.

Time charts or Timeline

Charts are one way in which we can write history. They show different things and these include:

• events which happened in the past
• The order in which they happened
• Centauries in which events happened
• Here is an example of timeline used to measure the historic periods of time from 3 million years before Christ (Paleolithic) to Contemporary Age (From French Revolution – 1789 up to now -2024)

A.D (Anno Domini)

• It’s a Latin word that means ‘Our Lord’ or ‘after the birth of Jesus Christ’.
• The dates of all events that happened after the birth of Jesus Christ are written with A.D in front of them; they are measured forward after the birth of Christ .E.g. AD 1835 the Ngonis crossed the river.

B.C ( Before Christ)

• This means before the birth of Christ
• All the events that happened before the birth of Christ are written with the letters B.C in front of them e.g. BC 560
• Note: However most scholars prefer the order of writing starting with the year ending with the letter AD or BC. This is not wrong.

How to calculate years ago for A.D

Years ago, for A.D are calculated by subtracting the year given from the year now.
How to calculate years ago for A.D For example: How many years ago is 1835?
2013 – 1835 = 175 years ago
NOTE: Subtract the year given (2013) from the year now (1835).

How to calculate years ago for B.C.

B.C means ‘Before the birth of Jesus Christ
All the events that happened before the birth of Christ are written with the letters B.C in front of them. B.C 752

How to calculate years ago for B.C

Time before the birth of Christ is counted backwards.
The years ago, for B.C are calculated by adding the year when the event happened to the year now.
For example: How many years ago is B.C 752?
2013 + 752 = 2770 years ago.

How to convert years into centuries.

Divide a year given by 100
Add 1 to the answer found, ignoring the decimal point.
Example: In what century were the following years?
560
910
1620
1423

Solutions

560/100 =5.6
5 +1=6th century
910/100=9.1 9+1=10th century
1620/100=16.2
16 +1=17th century
1423/100=14.23
14 + 1=15th century

Other Historical Measuring Instruments of Time

Clock: an object that shows the time. The object like a clock that you wear on your wrist is called a watch. Clocks either have a background called a face with hands that point to the hours and minutes, or they are digital clocks that show the time as a set of numbers. You say a clock is slow when it shows a time that is earlier than the correct time. You say it is fast when it shows a time that is later than the correct time

Sundial: The sundial was invented in ancient Egypt and was also used in ancient China, Greece, and Rome. Sundials consist of a shadow-maker known as a gnomon, which casts a shadow onto a surface below, usually marked with the hour. As the sun moves through the sky, the shadow moves accordingly, indicating the time of day. Sundials are accurate to within a few minutes but must be adjusted for daylight savings time.

Atomic Clock: The atomic clock is the most accurate clock currently in use. The first atomic clock was built in 1949 at the United States. National Bureau of Standards (NBS). The first accurate atomic clock, based on the transition of the cesium-133 atom, was built by Louis Essen in 1955 at the National Physical Laboratory in the United Kingdom. This led to the internationally agreed definition of the second being based on atomic time.

The table below summarises the different instruments used to measure time and their accuracy.

Instruments	Accuracy(accuracy to the nearest)
Stop-clock Stopwatch Ticker-tape timer Electric stop-clock Digital timer Oscilloscope(CRO) Laser, atomic clock