What’s in a Calendar?
What is a calendar?
A calendar is a system for dividing time and arranging the divisions.
Kids and adults use calendars almost every day. Whether they hang on the wall or are opened with a tap on a cell phone, calendars help us keep track of appointments, school days, sporting events and other important dates.
Who invented the first calendar? Why do we have 24 hours in a day and 12 months in a year? The Mini Page found out more about how calendars were developed.
Where do we start?
In ancient times, people noted the passage of time by sunrises and sunsets, seasons and moon phases. For example, it takes about 24 hours for the Earth to make one rotation on its axis; this is the basis for a day.
Our calendar bases months roughly on the time between new moons. Can you remember how many days each month has?
29. has it year, leap a in days; 28 has February year, regular a In February. for except days, 31 have months other The November.” and June April, September, has days 30“ rhyme: this with has month each days many how remember can You Answer:
Reading the numbers
In the year 585 in Rome, a scholar named Dionysius invented a calendar that numbered the years. It used B.C. and A.D. to tell the difference between the years before and after the birth of Jesus Christ.*
B.C. stands for before Christ. If we say 225 B.C., we mean 225 years before Christ was born.
A.D. stands for anno domini, a Latin phrase meaning “the year of our Lord.” When we say A.D. 435, we mean 435 years after Christ’s birth.
In 1582, Pope Gregory XIII changed the calendar, and most people still use the Gregorian calendar today.
This calendar is based on how long the Earth takes to make one orbit around the sun. Today this is calculated as about 3651/ 4 days — which is why every four years, we have an extra (leap) day in February. * Today some people use B.C.E., or before common era, and C.E., or common era, to identify the years.