HOURS OF THE DAY
The earth, on turning one revolution in 24 hours, gives the impression that the sun "rises in the east" and "sets in the west". A complete revolution of the earth, of 360 degrees, is accomplished in 24 hours, thus the sun appears to move through the sky by 15 degrees per hour. In its course, it passes through its meridian ("Due South" for the inhabitants of the northern hemisphere -- "Due North" for the inhabitants of the southern hemisphere ), at noon, at all times of the year.
There is usually a difference in the length of day and night, depending on latitude and season. The extreme example of an arctic summer of 24 hour daylight, and an arctic winter of 24 hour darkness is well known. This is caused by the annual "wobble" of the earth, i.e. the change in the angle that the earth's North-South axis makes with arriving sunlight. This "wobble" completes a full oscillation once a year, and explains why there is a summer and a winter once a year outside the tropics. In the tropics the differences between length of day, and length of night, are less, but still exist. In the mid-latitudes of Europe, during the winter solstice, 21 Dec, the sun rises in the south east, is in the south at noon, and sets in the south west. At the equinox, 21 March and 21 Sept, it rises in the east, and sets in the west. In the summer solstice, 21st June, it rises in the north east, is in the south at noon, and sets in the north west. One result of this is that today, because our hours have a constant length, in northern France for example we may have 18 hours of daylight around the summer solstice, and only 6 hours of darkness, whilst in winter these figures are reversed.
It was very different in Palestine, at the time of Jesus. Days (daylight) and nights (darkness) were arbitrarily divided into 12 hours each. The sundial showed noon at noon, which by definition was the end of the 6th hour. Therefore the duration of each "Jewish" hour would obviously vary with the season; a winter "Jewish" hour lasted only 50 of our present-day minutes, while a summer "Jewish" hour lasted 70 of them.
As far as the Passion is concerned, it took place at the beginning of April, close to the Spring equinox, when the duration of the Jewish hour was about 60 minutes, close to the standard hour of today. The first hour would have been from approximately 6 to 7, the third hour, from 8 to 9, the 6th from 11 to noon, the 9th from 14.00 to 15.00hrs, and the end of the day which was also the end of daylight, occurred around 18.00 hrs. That is why the Sabbath started on Friday evening, around 18.00hrs, at the end of the 12th hour of day.
The Greek and Roman systems were very close, the days being counted in the same way, i.e. 12 hours between sunrise and sunset.
The sundial seems to have been known at least 250 years before Christ in this part of the world.