Up to the fourteenth century in Europe there were the same nunmber of nightime hours winter and summer. For example, the winter night would consist of 12 hours and the winter summer would consist of 12 hours. The length of each hour however would differ. During the winter, nightime hours were much longer, daytime hours were much shorter, in order to keep the total number of hours unchanged.
The reason for this in medieval europe was that hours were measured by their content, not their content by the hours. Time was determined by action, rather than being an 'objective' fact independent of the activities which filled it. Even when the mechanical clock was invented hours continued to be changeable, measured by their content rather than being a measure of their content.
(The content was primarily the content of the Church day.)
Then in anumber of cities in western europe workshops appeare staffed by wage workers, and in a few of these wages began to be paid by the hour. The mechaical clock was used to measure these hours. But the older variable hours continued to be used in monasteries, churches, and in general in rural areas. Mechanical clocks arrivbed in China but there were used merely as curiosities, for in China, as in ancient Greece and Rome and everyplace else time;, time was not a measure of its content but rather time was measured by its content.
In other words, time is not an obbective entity but is a social product.
I'll explore some other day some of the implications of this fact.
Carrol