Etymology of the word “calendar”

The word “calendar” has origins in several different languages. It is related to
Old French “calendier,” meaning list or register. It is also very closely related
to the Latin “calendarium,” meaning account book, as well as “calendae (kalendae)”
(plural of “calends”) from the first day of the Roman month.

About the calendar

The bases of the calendar are the day (one rotation of the Earth on its axis), the
month (one revolution of the moon around the Earth) and the year (one revolution
of the Earth around the Sun).

History of the calendar

Ancient people first used the moon cycle to measure time. Each time they saw the
moon, they would make a mark on a slate, cave wall, or some type of bone–each mark
represented one viewing of the moon, or what we currently know as a “night.” They
also would group these based on time passed between full moons–this is close to
what we call a “month” today.

Today we use the Gregorian calendar, but time has not always been measured this
accurately. Previous generations used the Julian calendar, which was very near the
length of an actual year, but it did not account for the slight shift in time year
after year. Measuring time was oftentimes not studied seriously, because it was
viewed as an invasion to God’s mysterious ways. In 1582, after the calendar had
become 10 days away from the actual date and time, Pope Gregory XIII changed the
calendar to accurately reflect the drift over time. From that point on, the measure
of time was considered more of a technical subject, and scholars researched and
studied it in a more serious manner. However, this new calendar was not met without
resistance. Certain sects of Christianity insisted that Pope Gregory was the Antichrist,
trying to mislead other Christians from maintaining certain holy days.

How we measure time

Today’s records of time are split into two major units: BCE (Before Common Era)
and CE (Common Era). These replaced the previously used terms BC (Before Christ)
and AD (Anno Domini, or In the year of our Lord). Time can also be measured in the

  • Millenium: 1,000 years
  • Century: 100 years
  • Decade: 10 years
  • Olympiad: 4 years
  • Year: 12 months, or 52 weeks, or 365 days (Leap Year: 366 days)
  • Month: Generally 30 or 31 days (depending on the month), or approximately four weeks
  • Week: seven days
  • Day: 24 hours
  • Hour: 60 minutes
  • Minute: 60 seconds
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