Created 3 years ago
Thirty days hath September...but why the heck does February have 29 every four years?
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Terms in this set (19)
Why do we have leap years?
The time it takes the earth to make one complete revolution around the sun is called a solar year. On average, a solar year takes 365 days, 5 hours, 48 minutes, and 46 seconds. You could round it and say that the year is 365 days, but that wouldn't make the extra time just go away... The extra time would accumulate, and you'd lose a full day every four years! After a while, the seasons wouldn't match the months. So, to make up for the extra time, we add an extra day to the calendar every four years.
What are the extra days called?
They're called leap days.
What are the years in which the leap days occur called?
They're called leap years.
Who made this practice official?
Julius Caesar, the Roman dictator, in 45 B.C.E.
Fact!
Caesar reformed the imprecise Roman calendar into the 12-month, 365 day format that we use today.
Did the new calendar the Caesar made include leap days every four years?
Yes.
What was the problem with his calendar?
It was that the calendar year still didn't match up with the solar year. Because of the error, the calendar was still gaining a full day every 128 years. After more than a thousand years, the extra day would begin to add up.
What is the vernal equinox?
The first day of spring.
What day was the vernal equinox supposed to fall on?
March 21, but by the late 1500s, it was moving closer and closer to February.
Fact #2
The lost time made it hard to set the dates of religious festivals.
Who announced that every 4 years there would be a leap year?
Pope Gregory XIII.
In which calendar did he make that change?
In the Gregorian calendar.
In what year did he make the change?
In 1582.
What was the one exception?
Years ending in "00" would not be leap years anymore, except if they were divisible by 400.
Fact #3
The system we use today is still not perfect, the calendar still loses a day every 3,200 years or so.