How did ancient civilization tell the time? How did ancient people know different months?

A number
of ancient civilizations relied on the observation of celestial bodies. By plotting the
alignment of the stars and other heavenly bodies, the ancients were able to organize their
lives. The Greeks, for example, used the stars to help them determine which time of year was
best for farming or embarking on sea voyages. As these were essential activities for the
stability and health of the community, it was important to achieve some degree of accuracy.
Contrary to what we might think today, some of the instruments used by the ancients for
measuring time were really quite sophisticated. An example of this is the Egyptian Antikythera
Mechanism, a complex device consisting of wheels and gears that measured the movement of
celestial bodies.

The growth of mathematics as a discipline allowed the
Greeks to achieve more accuracy in the measurement of time. The Greeks began to gain a better
understanding of angles and so devised a series of sundials that could measure time in a greater
number of different locations. This important technological development allowed, in due course,
the Romans to make portable sundials, which proved particularly useful on their seemingly
endless military campaigns.