In the earliest times, human beings calculated time by observing the periods of light and darkness that alternated continuously. The solar day is considered the earliest form of the calendar. The second basic type of calendar was the arbitrary calendar, which was created by counting the number of days over and over again, either towards infinity or in a cycle. Nonetheless, there were several problems with the arbitrary calendar.
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Firstly, farmers of early civilizations could not calculate the perfect time to plant their crops. Crop planting is an activity that is closely linked to the seasons, and the arbitrary calendar was not based on the durations of seasons.