The Rishis, measuring time, have given particular names to particular portions. Five and ten winks of the eye make what is called a Kashtha: Thirty Kashthas make what is called a Kala. Thirty Kalas, with the tenth part of a Kala, make a Muhurta. Thirty Muhurtas make up one day and night. Thirty days and nights form a month, and twelve months form a year. Persons well-read in mathematical science say that a year is made up of two solar motions. viz., the northern and the southern.