Astronomy Group
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pohnpei397 Teacher
Community / Jr. CollegeeNotes Editor
Posted by pohnpei397 on Wednesday October 21, 2009 at 7:12 PMThe 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.
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krishna-agrawala Teacher
Graduate SchooleNotes Editor
Posted by krishna-agrawala on Wednesday October 21, 2009 at 10:54 PMCalendar 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.
