The ancient way of measuring time was as follows. The time taken by a needle to pierce a leaf was 1 alpakala. 30 alpakalas made a truti, 30 trutis a kala, 30 kalas a kashta, 30 kashtas a nimisha, 4 nimishas a ganita, 10 ganitas a sigh, 6 sighs a vinanazhika, 6 vinanazhikas a ghadika, and 60 ghadikas a day (ahoratra).

15 ahoratras make a paksha, 2 pakshas a chandramasa (ahoratra for pitrs), 2 chandramasa a rithu, six rithus a manushyavarsha (1 ahoratra for devas), 300 manushyavarshas make a devavarsha (divyavarsha), 4800 divyavarshas a Kritayuga, 3600 divyavarshas a Tretayuga, 2400 divyavarshas a Dwaparayuga, 1200 divyavarshas a Kaliyuga. 12000 divyavarshas make a Chaturyuga, 71 Chaturyugas make a Manvantara. 14 manvantaras make a Kalpa (pralaya). 1 Pralaya is a morning for Brahma, as per Bhagavata Tritiyaskanda.

7.5 nazhikas make a yama, 4 yamas a morning, and 8 yamas a day as per Devibhagavata Navamaskanda.

However the measurements given in Vishnupurana vary from this. As per Vishnupurana Ansh 1 Chapter 3, 15 nimishas make a kashta, 30 kashtas a kala, 30 kalas a muhurta, 30 muhurtas make a day for manushya. 30 days make a month (masa), 6 months an ayana, an uttarayana and a dakshinayana make a year. The dakshinayana is a night (ratri) for devas and uttarayana a morning. 12000 divyavarshas (year for devas) make up a chaturyuga made up of Kritayuga, Tretayuga, Dwaparayuga and Kaliyuga, of 4000, 3000, 2000, and 1000 divyavarshas separated 400, 300, 200, 100 year gap before and after each respectively. The interval before the start of the cycle is called Sandhya and the period at the end is the Sandhyansh. A thousand chaturyugas is a day for Brahma. In that day are 14 manvantaras.

As per Vishnupurana Ansh 2 Chapter 8, 15 nimishas make a kashta, 30 kashtas a kala, 30 kalas a muhurta, 30 muhurtas an ahoratra, Though the length of the day and night vary with the splitting of Purvahna, Madhyahna, Aparahna, the Sandhyakala remains 1 muhurta (2 nazhikas). From Surya’s ardhodaya (the time it rises) to 3 muhurtas thenceforth is Pratahkala. This is 1/5th of the morning. The three muhurtas following this are called sangava, and then 3 muhurtas called madhyahna. The next 3 muhurtas make up aparahna followed by sayahna. The length of these vary in uttarayana and dakshinayana. On one day of the year, they are exactly equal. 15 ahoratras make a paksha and 2 pakshas a month. (masa) 2 sauramasa make a rithu and 3 rithus an ayana. 2 ayanas make a year. (varsha) There are four kinds of months – saura, savana, chandra, nakshatra and five kinds of varshas – samvatsara, parivatsara, idvatsara, anuvatsara, and vatsara. These 5 make a yuga and it contains 60 sauramasa, 61 savanamasa, 62 chandramasas, and 67 nakshatramasas.