# Calendar

Who invented the first calendar? Why do we have a leap year?

pohnpei397 | Certified Educator

The question of who invented the first calendar is very hard to answer -- no one knows for sure.  Many ancient societies had them.  The Egyptians are, however, credited with the first solar calendar (based on the sun as opposed to on the cycles of the moon).

The reason we have a leap year is much easier...  As you know, a year is defined as the time it takes the earth to complete one orbit of the sun.  Sadly, the earth doesn't take a whole number of days to orbit but instead takes 365.25 days to orbit the sun.

So, every four years we add an extra day to make up for the fact that our year is actually one-quarter day shorter than it should be.

atyourservice | Student

It isnt sure to say who was the first to invent the calender as there were a lot of cultures known to have a calender. The reason for the leap year is because it doesn't take exactly 365 days for the earth to rotate around the sun but 365.25 so the extra day in February every 4 years makes up for that slight difference.

Wiggin42 | Student

This is quite a difficult question because new evidence is being discovered all the time. As of 2013, there has been a discovery that the people of northern Scotland had a crude lunar calendar made of stone blocks that dates back to 8000 BCE. That is the mesolithic era.

A leap year occurs because every year is actually comprised of roughly 365.25 days. So, every four years, those extra .25 days come together to make up an actual day so we add that extra day in. If we did not, over time our time-keeping wouldn't match with our revolution around the sun.

astrosonuthird | Student

The first calender was invented by the Greeks. We have a leap year because,

LOOK --

one day insint 24 hours, one day = 23 hours, 56 minutes and 4 seconds. After 4 years, the remaining of 23 hours, 56 minutes and 4 seconds become complete and thus form a exxtra day which comes as February 29. It is called a leap year.

Earth is slowing down and one day we will not have a leap year.

krishna-agrawala | Student

Calendar is a system of measuring and recording times in terms of days and years. Many different types of calendar were developed and used by people in different parts of the world. Exact knowledge about many of these calendars is lost. The oldest calender about which information exists is perhaps the Hebrew calendar.

The Hebrew calendar started 3760 years and 3 months before christian era. This calendar is based on lunar movement. One year in this calendar consists of 12 months which are alternatively 29 and 30 days long. Seven times during every 19 year period and extra month of 29 days is added to keep the calendar year and the real solar year in line.

Egyptians started using a calender much before the Start of Hebrew calendar. Their calendar was based on the solar system. According to experts the earliest known date according to Egyptian calendar is 4236 B.C.

terrence958 | Student

I believe that the Mayans made the first calender and they all of a sudden, stopped at 2012....Woah....

As for leap year...I don't know sorry...

but check this website