A Study in Time

From The American Horologist magazine, May 1946

A Study in Time
By Ted Douglas

The time we live by is known as civil time and is based on the apparent motion of the sun over the earth. This motion of the sun is too irregular to permit the construction of clocks set to follow the sun exactly. Such a clock would have to tick off less than 60 minutes for some hours of the day, and more than 60 minutes for others.

Our 24-hour day, with each of its hours containing 60 minutes, is arrived at by means of averages. For our convenience, we have worked out the idea of an average sun which apparently moves across the earth with a regular rate equal to the average rate of the true sun's movement.

If we could see both the true sun and our average sun in the heavens, the two would be in exactly the same position at only four instants during the year, although they never would be very far apart.

The division of the earth into 24 time zones is another idea based on averages. It saves us untold inconveniences, and makes possible the conditions by which we can accurately compute time by our clocks and watches.