Sanle calendar

The Sanle calendar is an obsolete lunisolar calendar once used by the Sanle Empire and areas under their influence.

Year lengths

Years contained either 13 months or 14 months. Years containing the 14th month were determined according to an 86-year cycle called the Large Sun Cycle which, in turn, was based on a 21-year cycle, called the Small Sun Cycle. In the Small Sun Cycle, the 2nd, 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th, and 20th years had 14 months. After every 4th Small Sun Cycle, two additional years were added, the first 13 month the second 14 months, to make the 86-year Large Sun Cycle.

Month lengths

Most months were 18 days. The 3rd and 9th months were 19 days, while the 6th month was usually 18 days but sometimes 19 days. Its length was determined by a set of nested cycles. The first was the 7-year Small Lunar Cycle. In the Small Cycle, the 2nd and 5th years had a long 6th month. Sixteen of these made up the 112-year Large Lunar Cycle. In the 16th Small Cycle, the 5th year had a short 6th month. 10 Large Cycles in turn made a Grand Cycle (1,120 years). In the 10th Large Cycle, the 16th Small Cycle had a long month in the 2nd and 5th years

Month names

The months were simply numbered, although various names were sometimes used for different months in different areas. There was no united naming system, however, and thus the months are generally referred to by numbers.

Accuracy

The Sanle calendar has a very high degree of accuracy. On average, the lunar months are accurate to about 1 day every 80,000 year or so, although this is only an average and in the short term, the months be a day or so off one way or the other. The months gradually drift relative to the seasons by about one day every 2800 years, although, due to precession, this is dwarfed on a practical timescale by changes in seasonal lengths.