Vishnupurana 2.8.p10

2.8.p10

Fifteen Nimeshas (twinkling of the eye) make a Kāshthā; thirty Kāshthās make one Kalā; thirty Kalās a Muhurtta and thirty Muhurttas a day and night; the divisions of the day become longer or shorter in the way explained before. But as regards increase or decrease Sandhyā is always the same for it is only one Muhurtta. From the time when half of the sun's orb is visible to the expiration of three Muhurttas the interval is called Prātar (morning) forming a fifth portion of the day. The next portion or three Muhurttas from morning is called Sangava (forenoon); the three next Muhurttas make the midday; the three next Muhurttas constitute the afternoon; the three next Muhurttas make the evening; and thus the fifteen Muhurttas of the day are divided into five portions of three each. But the day comprises fifteen Muhurttas only at the Equinoxes and increases and diminishes in number as the sun declines towards the north or the south, when the day encroaches upon the night and the night upon the day. The equinoxes take place during the spring and autumn when the sun enters the signs of Aries and Libra. When the sun enters Capricorn his progress towards the north begins and when he enters Cancer his progress towards the south commences. Fifteen days of thirty Muharttas each are called a Paksha (fortnight); two fortnights make one month and two months a solar season and three seasons make one Ayana (a northern or southern declination) and two Ayanas make one year. Years are made up of four kinds of months and five years make one Yuga or cycle. The years are respectively called Samvatsara, Parivatsara, Idvatsara, Anuvatsara and Vatsara. This is the time called a Yuga.