Analysis of information sources in references of the Wikipedia article "Metonic cycle" in English language version.
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What is especially fascinating is the ornamentation on the [Berlin gold hat] in which a complex counting system is encoded, enabling calendar calculations, especially the 19-year cycle of the sun and the moon. ... The star at the tip symbolises the sun, with the sickles and eye patterns representing the moon and Venus, while the circular ornaments can equally be interpreted as depictions of the sun or the moon. … The cycle of the sun determines day and nigh and the seasons, while the moon determines the division of the year into months and days. But the lunar year is eleven days shorter than the solar year. Even as early as the 2nd millennium BC intercalary days were inserted to bring the solar and lunar cycles into alignment. This knowledge is reflected in the ornamentation of the Gold Hat. The stamped patterns should be read as a calendar. For instance, the number of circles in certain decorative areas equals the twelve lunar periods of 354 days. If the patterns in other decorative areas are added, this gives the 365 days of the solar year. It takes 19 years for the solar year and the lunar year to align again. In the ornamentation of the hat the fact is encoded that seven lunar months need to be inserted into the 19-year cycle. Other calculations can be made as well, such as the dates of eclipses of the moon. (…) The golden hats show that astronomical knowledge was combined with cult activities… They were apparently worn over several generation and at some point buried in the ground in a sacred act to protect them from desecration and to place them in the realm of the gods. It seems that Bronze Age rulers combined worldly and spiritual power.
One particularly impressive piece of evidence for early man's astronomical knowledge is the Bronze Age Berlin gold hat, unique in its size and preservation. The sun, evoked by the gold coloration and the pattern of rays at the top of the hat, creates day, night and the seasons by apparently circling the earth. The moon, represented several times on the hat, marks out months and weeks. The number and arrangement of the ornaments is not random; it allows a nineteen-year lunisolar cycle of 228 solar months and 235 lunar months to be calculated. Someone who knew how to read these ornaments would be able to calculate the shifts between the solar year and the lunar year, predict lunar eclipses, and set fixed dates for significant events. … Over half a millennium before the astronomer and mathematician Meton in 432 BC calculated the shifts in the lunisolar cycle, they were already known to the educated elite of the Bronze Age. The golden hat may have been worn by a ruler with a religious role on ceremonial occasions. Other Bronze Age items prove that astronomical knowledge was often preserved in coded form on valuable and sacred objects.
