Historically we have been able to gather only a little knowledge about the methods of time keeping in prehistoric eras, but we do know that in practically every culture just as today, people have been preoccupied with measuring and recording the passage of time. The celestial bodies of the Sun, Moon, Planets and Stars, have allowed ancient civilisations to create systems to provide a measuring of seasons, months, and years.
In Europe we have discovered archaeological finds which indicate that over 20,000 years ago scratched lines on sticks and bones, or carefully gouged holes were used as ancient calendars, believed by academics to demonstrate ways of indicating the days between phases of the moon, 'lunar cycles'. Around five thousand years ago, the ancient Sumerians, in the Tigris-Euphrates valley (now in Iraq), had a highly developed system :
each year was divided into months;
each month consisted of thirty days;
each day was divided into twelve periods (each period has been calculated to be roughly equivalent to two hours by today's time measurement);
each two hour period consisted of thirty parts (calculated to be roughly equivalent to four minutes by today's measurement)
No written records exist relating to the ancient sacred site of Stonehenge, built over 4000 years ago in England (UK), but it has been suggested that the alignments indicate it was used to measure 'seasonal' or 'celestial changes'. It is believed that these measurements were used to inform the time setting of rituals and events, and possibly further used to indicate when crop planting, harvests or festivals could start.
The earliest Egyptian calendar known is believed to be based upon lunar cycles The ancient Egyptians later recognised, and it is thought discovered, the 'Dog Star' in 'Canis Major', which we now call 'Sirius'. The Dog Star rose alongside the Sun every 365 days. It is believed from this the 365-day calendar was devised, with approximate dating of this development to 4236 BC. This is a significant date, as historians claim that this is probably the earliest recorded year in the history of time.
Approximately 2000 BC the ancient Babylonians formulated a system based on lunar cycles of;
a year, calculated to be of 354-days duration;
a year structured on 12 lunar months;
the length of the month alternated, consisting of either a 29-day or 30-day period.
The Mayans, of Central America, however used a combination of influences to calculate their calendar. The year was devised according to journey of the Sun, the Lunar cycle and the planet Venus. This calculation produced two calendars; the first was of 260-days duration, and the second of 365-days. It is believed that this calendar influenced the development of the Mayan culture from around 2000 BC - 1500 AD. Examination of ancient records give 3113 BC as the date for Creation of the Earth. With scientific progress we now know that this is highly unlikely but perhaps Creation should be interpreted according to Mayan beliefs on the planet and the universe. The Mayan system was later used in sections of the great Aztec calendar stones.
The Mohammedan Calendar is known to have been in operation since the day of the Hegira', 16 July, 662 AD. This calendar is made up of twelve lunar months, with each month calculated to twenty-nine days + twelve hours + forty-four minutes.
Other civilisations, like those in the Western hemisphere such as our own, adopted a 365-day solar calendar allowing a leap year every fourth year. The 'Julian Calendar' was introduced in 46 BC, fixing the year to 365 days, and as highlighted, including an extra day every fourth year. This was later modified for the 'Gregorian Year', also known as the 'New Style' which was introduced in 1582 (taken on in the British Isles as late as 1752). Pope Gregory XIII was responsible for its introduction and formulation, which gave rise to the standardisation of many Christian feast days.
The first of each month was known as the 'Calends' by the Romans, which is perhaps why the name given to describe the full cycle of the year is known as the 'calendar'. This Roman term 'calends' is known to have meant 'the coming together', 'the meeting' of people, which always occurred on the first day of the month. The 'Pontifex', the head of the college of sacred priests, would then inform the people of which dates within the month were to be sacred, days given to festivals or the new moon.
'Time is, time was, time's past.' Byron, Don Juan.