the hours of sunlight into 12 hours, but, obviously, in northern latitudes an hour dur-
ing a long summer day might be twice as long as an hour during a short winter day.
The Western civil calendar that is now used internationally is based on hours of a pre-
cisely defined fixed length, but there are still some local or folk calendars in which the
length of an hour is much more flexible.
The next most obvious way to divide time is to use the phases of the Moon.
Originally, a month was a “moonth”: It represented the period from one full moon or
new moon to the next. We cannot know how people measured time during the tens or
hundreds of millennia that all human beings existed as bands of hunters and gatherers,
following the herds and the ripening fruits and grains in an annual migration north
and south. During the last ice age (from roughly 20,000 to 100,000 years ago), when
human beings were forced to live in caves and develop new stoneware technology in
order to survive, they may have begun tallying the phases of the Moon more carefully
than before in attempting to calculate the length of the lunar month. In the Western
civil calendar, months are arbitrary groups of days, ranging from 28 to 31 days in
length that are not correlated with the phases of the moon. All major religious calen-
dars (Christian, Jewish, Moslem, Buddhist, and Hindu) still depend wholly or partly
on having months that are exactly in phase with the Moon.
The third most obvious time division is marked by the seasons—the annual
migration north and south of the Sun’s rising and setting points. Probably for a long
time, years were labeled only relatively, as the regnal year of a king, by the number of
years since some memorable event, and so on; and this starting point would be
changed with every new generation. Only rather late in the history of civilization did
years begin to be numbered from some fixed point in the distant past, such as the first
Olympiad, the founding of the city of Rome, or the birth of Jesus of Nazareth.
Constructing a CalendarAs could their predecessors, agricultural villagers today can coordinate their annual
activities by word of mouth, but citizens of an empire cannot. It obviously will not work
to have the arrival times of people coming to a three-day festival in the capital city
spread out over a week. Hence, about 5,000 years ago, the administrators in Egypt and
Sumeria were faced with the problem of constructing a calendar that everyone could
use to see, on each day, how many more days it would be until some scheduled event.
But to construct such a calendar, these people had to deal with four basic questions:,
- How long is a day?
- How long is a month? (Or, equivalently, how many days are there in a
month?) - How long is a year?
- How many months are in a year?
Being used to our modern answers to these questions, we may think them
obvious; but they are not, and adequate answers to them were found only by centuries
of ongoing observations, measurements, and calculations.
THEASTROLOGYBOOK [109]
Calendar