Book of Indian Eras, with Tables for Calculating Indian Dates c5.4

c5.4

But the great difference of 11 days between 12 lunations and 1 revolution of the sun must soon have led to the establishment of the old cycle of 5 solar years and 62 lunations. Taking the solar year at 365¼ days, and the moon's revolution at 29½ days, the 5 solar years would have been 1826¼ days, while the 62 lunations would have been 1829 days. The difference of 2¾ days in the lustrum of 5 years would have made a yearly difference of upwards of half a day. The five years consisted of three ordinary years of 12 lunar months, and of two years, the 2nd and 5th, each with an intercalary, or thirteenth month.