Since the remote Antiquity the mankind reckoned time. About 30,000 BC, carved bones were produced on which several notches, phased per the number of days of the synodic lunar month, were engraved. These bones were used to plan hunting. So, the Moon was the more ancient astronomical “target” taken in account to forecast the (short term) future.
Image: aerial view of Stonehenge megalithic site in England (public domain, source: Britannia Internet Magazine).
During the Neolithic and Copper Ages, the so called Megalithic People built great geometrical structures made with heavy stones to mark some relevant astronomical directions in which the Sun and the Moon rise and set at the local skyline. The aim was to sacralise that lines and to reckon time to plan agriculture, breeding and farming.
During the Bronze Age, there were the initial attempts to phase the periods of the Sun and the Moon developing the first codified calendars. In this time the observation of the rising and of the setting of the stars became important and during the following Iron Age the time based on the observation of the heliacal rising and setting of the bright stars was the main method for reckoning time. In this era, the Celts developed the very sophisticated Calendar of Coligny coding the solar and the lunar cycles into a very nice five-years structure, with a 2.5-years intercalation scheme. The Roman civilization produced the Julian calendar (after Julius Caesar), a purely solar one, adopted by Christianity along the Middle Age and the Renaissance until the Gregorian reform ordered by pope Gregory XIII in 1582. This reformed calendar is the actual one.
Reckoning time and short term future prediction were, through the centuries, a social activity developed by priest and sacred people because of the lack of a real understanding of the essence of the “Time”; so, time-reckoning had great political importance among all the ancient cultures. Since in ancient epochs the effective reckoning of time was likely impossible without performing astronomical observations, in fact Astronomy had a strong impact on the political and social environment from the Palaeolithic age up to recent times.
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