The Sumerian calendar - Artist view - The Moon and sixty - Artist view -...

The Sumerian calendar - Artist view - The Moon and sixty - Artist view - Artist view of a crescent moon above a Sumerian temple. The Sumerian calendar was 360 days a year and was based on the phases of the Moon. Sixty, not ten, was the basis of Sumerian math. The Sumerian calendar, the farming 'tool - kit', was based on the phases of the Moon; 12 x 29.5 days. This produced a year equal to 360 days; a reasonable approximation, but not accurate over time. Every so many years an extra month had to be added, and an incredibly complex math system was used to make the adjustment