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| Oh remember how short my time is:
For what vanity hast thou created all the children of men! Ps 89:47 |
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TIME fact 4:TIME: part 4
of 9
Division of the year into months and days is the major time measurement for humans.
For the past couple of days "Facts" has presented some different calendars. Some
of these were ancient calendars, some are still in use today. Calendars have generally
been developed around the phases of the moon for months. The year is often seasonal and
based on a solar year. The problem has been in relating the lunar calendar with the solar
calendar.
Coptic calendar - A calendar that is still used in parts of Egypt and Ethiopia. This
calendar is very similar to the Egyptian calendar. There are 12 months of 30 days followed
by 5 complementary days .When a leap day occurs, an extra day is added to the
complementary days for a total of six.
Roman calendar - A calendar that borrowed heavily from the ancient Greek calendar. The
calendar of the ancient Greeks had a four year cycle based on the Olympic Games. The
earliest Roman calendar dates from about 738 BC. It was a 10 month calendar with a total
of 304 days. Every second year a short month of 22 or 23 days was added to keep the
calendar coinciding with the solar year. Eventually two more months were added at the end
of the year. The addition of Januarius and Febuarius increased to days in a year to 355.
During the reign of Tarquinius Priscus (616-579 BC) a lunar calendar, the republican
calendar, replaced the earlier calendar. This calendar had 355 days, with the month of
February having 28 days. The remaining 11 months had either 29 or 31 days. Every two years
an extra month was added to the calendar. The republican calendar was later replaced with
the Julian calendar. By the time the Julian calendar was used the republican calendar was
a full three months ahead of the seasons (solar year).
Julian calendar - In 46 BC, Julius Caesar wanted one calendar to be used by all of the
empire. He had the astronomer Sosigenes develop a uniform solar calendar. This calendar
established a year of 12 months of 30 or 31 days except for February which had 28 days.
The year consisted of 365 days. To compensate for a true solar year a leap day was added
to February every four years. The first day of the year was moved from March 1 to January
1.
Gregorian calendar - Pope Gregory XIII instituted calendar reform in 1582. His goal was to
align the celebration of Easter with the vernal equinox which is the first day of spring.
To better align the solar calendar with the seasons, the new calendar would not have leap
year in the century years not divisible by 400. This is the calendar in use by much of the
world today. To keep this calendar in line with the shortening true solar year, a leap
second adjustment is added when necessary at midnight on December 31.
Japanese calendar - This calendar has the same structure as the Gregorian calendar. There
are the same number of days, months and weeks in a year. The years, however, are
enumerated in terms of the reigns of emperors as epochs. The current epoch started January
8, 1989. It is the Epoch Heisei for emperor Akihito.
Sources: The Handy Science Answer Book - Visible Ink |
