Measurements and subdivisions of the hours of a day in the Roman army

The roman army had specific moments of the day for wake up, eat, march and sleep.
The night was divided into four equal parts of three hours each: vigilia prima, vigilia seconda, vigilia tertia and vigilia quartia.

The day was divided into twelve hours, starting from the sunrise.
The measure of one hour was given by a sundial in the morning and by a hourglass during night.
In at last two cases we have found the words "horologium" and "horologiarius" to indicate, with the first, the official clock, and, with the second, the soldier/s who had to build it or to look at it.


Source: Professor George Cupcea study