The image of a medieval water clock (clepsydrae) from an illuminated manuscript.
Before the mechanical clock was developed at the end of the 13th century, the hours of the day were not fixed. Time was measured by sundials, hourglasses, special candles, or water clocks, none of which were particularly exact. Sundials didn’t work after dark, or in bad weather. Water clocks had to be regularly fed fresh water–in the heat of summer, the water would evaporate. In the cold of winter, the water froze making the clock useless. It is no wonder that the measurement of time was often a point of contention.
Dates were important to the educated for the purposes of law and historical documentation. The monks wanted to ensure their hourly calls to prayer were punctual. But the average person had little interest in chronology. The exact time of day did not have much relevance, and seasons as a whole were more important than specific months. Most would not have known their own birth year.
The most important cycle of time was the rising and setting of the sun, around which each day’s activities revolved. Summer days were longer than winter days; the workday began at sunrise, and ended at sunset. Tallow candles (the most common type) gave off such poor light it was difficult to do much of anything after dark. Church bells were rung to tell everyone within hearing distance when they should wake up, work, pray, and sleep.