un texte ici

The calendar

Leap years

In 46 B.C., the Egyptian astronomer Sosigene of Alexandria noticed that the Earth circled the sun in 365.25 days. What is the difference between his figure
and the standard 365 days that we normally use?

What does this difference amount to after 4 years?

Sosigene therefore advised Julius Caesar to follow these two rules to keep
the Julian Calendar accurate :

1.Years divisible by 4 should be 366 days long
2.The other years should be 365 days long
4 months of 30 days, 7 months of 31 days and 1 month of 28 days.

At the time, the extra day was inserted between the 24^th and 25^th of February .
Since February was considered to be a month of bad omens, it was out of the question for it to have an odd number of days.

Which of these important years were leap years?

622 Hegira
800 Charlemagne
1066 Hastings
1492 Colombus
1776 Declaration of Independance
1815 Waterloo
1945 Hiroshima

The solar year is actually 365.2422 days long, not 365.25 days.

Calculate the difference.

What does this difference amount to after 400 years?

By 1582, the gap had become so great that Pope Gregory XIII decided to go directly from Thursday the 4^th October to Friday the 15^th October. He added two further rules to the Julian Calendar, resulting in

the Gregorian Calendar that we use today :

Years divisible by 100 are not leap years
Years divisible by 400 are leap years

Which of these years were leap years?

1600
1700
1800
1900
2000

With this calendar, one year lasts 365.2425 days.

What will the difference be after 10,000 years?
(solar year = 365.2422 days)