Why are there 12 hours in a day? Why not 10 or 15? Who decided on the numbers
we see on the faces of most of our watches and clocks? It was the ancient
Babylonian star gazers, the first astrologers and astronomers. They divided
the stars along the path the sun apparently follows across the heavens into 12
groups we now call the signs of the Zodiac. Then they divided the day into 12
hours to match the Zodiac.
It proved to be such a reasonable and useful division of the daylight hours
that we still use it today, thousands of years later. You can thank some long
dead Babylonian for the numbers on the face of your watch, if it has a dial.
Nothing lasts like a good idea which helps in our daily lives.
The logical Greeks later decided there must also be 12 hours in the night, if
there were 12 hours in the day. So we got the 24 hour day and night.
A Greek mathematician, living in Egypt, then divided each hour into 60 minutes,
and each minute into 60 seconds. No one knows today why he picked the number
60. It may have had some mystical, or magical, significance for him. It
should be noted that the ancient Babylonians used a base 60 numbering system,
and this may have influenced the decision. In any event, the number he chose
proved very useful. It is divisible by many other numbers: 1, 2, 3, 4, 5, 6,
10, 12, 15, 20 and 30. So we still use the 60-minute hour, and the 60-second
minute today.
Greenwich Mean Time
Greenwich Mean Time (GMT) is the mean solar time at the Royal Greenwich
Observatory in Greenwich, England. With the growth of Britain as a maritime
nation, mariners kept their timepieces on GMT in order to calculate their
longtitude "from the Greenwich meridian". This eventually led to GMT being used
world-wide as a reference time independent of location. All time zones are
based upon this reference as a number of hours and half-hours "ahead of GMT" or
"behind GMT".
In 1884 at a conference held in Washington, the meridian passing through
Greenwich was adopted as the initial or prime meridian for longitude and
timekeeping. Given a 24-hour day and 360 degrees of longitude around the earth,
the world's 24 time zones are 15 degrees wide. The individual zone boundaries
are not straight, however. They have been adjusted for the convenience and
desires of local populations.
