THE CALENDAR

THE CALENDAR

Read the passage.

          It is easy to understand the calendar we use today.It was not always so easy. People had to try for thousands of years before they knew how to put together days, weeks, months, and years.

More than 2,000 years ago, scientists in Egypt made a calendar. There were ten days in a week, three weeks in a month, and twelve months in a year. This calendar showed a way to count weeks and months, but it was not scientific.

          It does not matter how many days are in a week, or in a month; any number can be used.No one, however, can decide how long a day or a year should be. A day is the exact length of time it takes the earth to turn around one time. A year is the length of time the earth takes to travel around the sun one time. The Egyptians did not think about these scientific facts. For them, 12 of their 30-day months made a year, but 360 days do not make a full year.

          What did they do about this problem? They made a five-day holiday at the end of each year. But even adding five holidays did not make the Egyptians' yearly calendar right. It takes the earth a little more than 365 days to travel around the sun. To be exact, it takes 365 days, 5 hours, 48 minutes and 46seconds.For a long time people did not add these extra hours and minutes and seconds.

          It was like using a watch that runs slow. The Egyptian calendar was slower than the exact sun year. In four years it was about a day behind; in forty years the calendar was 10 days (a full Egyptian week) behind the sun.

          Many years later in Rome, Julius Caesar tried to fix the calendar. He thought that a year should be 365 days and 6 hours long. He added an extra day every four years. The year with an extra day is called leap year. The year is really, 365 days, 5 hours, 48 minutes and 46 seconds long.Julius Caesar's calendar was almost twelve minutes too fast. Twelve minutes is not much, but by the year 1582 scientists showed that the calendar was about 10 days faster than the sun. Pope Gregory XIII wanted to make a better plan.

It was easy to take 10 days away from the calendar.  This made it right with the sun again. There was still a problem: how to keep the calendar right in the future, year after year.

          Scientists tried one way, and then they tried another. Finally, they decided to continue to have every fourth year as a leap year. Then they solved the problem of the calendar going too fast. They made a plan to take out three days every 400 years. A year ending in 00 is not a leap year unless it can be divided evenly by 400. The year 1600 was a leap year, but 1700, 1800 and 1900 were not. The year 2000 will be a leap year.

          This is the plan we use now. Our calendar, named for Pope Gregory, is called the Gregorian Calendar. It is not quite exact. It is 26 seconds fast each year by the sun time. Our calendar will not be fast by a whole day for at least 3,000 years.