New York State Test Prep Social Studies 5 (Grade 3) New York State Test Prep Social Studies 5 (Grade 3) World Communities

How do we measure time? We can begin by counting back the number of years. A year is made up of 365 days. However, we can measure time in larger units than just years. Let's take a look at a few ways of measuring time.

41williamjclinton.jpg - William Clinton
President Bill Clinton 1993

A decade is a period of ten years. If you are ten years old, you have lived for one decade. We can also count back through time by decades. In 1993, Bill Clinton became the President of the United States. That happened one decade ago. In 1983, Sally Ride became the first woman in space. 1983, was two decades ago. If your mom or dad is 40 years old, how many decades has he or she lived?

Let's try another question. Eight-year-old Carlos has two brothers, Pablo and Juan. Pablo is nine years old, and Juan is eleven. Which of the three brothers has lived for one decade?

wrightflyer04.jpg - Wright Flyer in the Smithsonian Institution.
Wright brothers airplane 1903

You know a decade is a period of ten years. Do you know what a period of 100 years is called? The answer is a century. A century is 100 years, or ten decades. What happened one century ago? The Wright brothers flew the very first airplane in 1903! Much has changed in one century. A century ago, most people did not even have electric lights in their homes or drive cars.

Actor George Burns lived to be 100 years old

Have you ever heard of anyone that has lived for a century? If so, that person would be a centenarian. A centenarian is a person who is at least 100 years old.

Declaration of Independence Stone Engraving
Declaration of Independence

The United States of America was founded in the year 1776, with the writing of the Declaration of Independence. Can you figure out how many centuries, decades, and years ago that was? Let's count back to that time in centuries, decades, and years from 2003.

One century ago was

Two centuries ago was

Three centuries ago was

Three centuries is too far back, isn't it? 1703 is before 1776, so we can only count back two centuries to the year 1803. Now let's count back by decades from 1803.

One decade before 1803 was

Two decades before 1803 was

Three decades before 1803 was

Three decades is too far back, isn't it? 1773 is before 1776, so we can only count back two decades to the year 1783.

Now let's count back by years. We can do this by subtracting 1783 - 1776 = 7. We can also count back year by year from 1783 to 1776. 1782 is one year before. 1781 is two years back. 1780 would be three years. 1779 is four years before. 1778 would make it five years. 1777 is six, and 1776 is seven years before 1783.

Altogether we have two centuries, two decades, and seven years ago that the United States was born.

We also have a name for a period of 1000 years. 1000 years is called a millennium. A millennium would be the equal to 10 centuries, or 100 decades. A millennium is a very long time, compared to a century or a decade. If we traveled back in time 1000 years ago, to the year 1003, we would find a very different world. The only people living on the continent of North America in 1003 were Native American groups.

Do you ever think about the future? What do you suppose life will be like a decade from now? How do you think it will change over the next century? What will the future bring a millennium from now?

Let's Review:

Year	a period of 365 days; we are living in the year 2003
Decade	a period of 10 years
Century	a period of 100 years
Millennium	a period of 1000 years

Let's Practice with a Game

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