The division of time
The serial of time - division given in Vedang Jyotish is appended below :-
10 Matra = 1 Kashtha, 124 Kashtha = Kala
10+1/20 Kala = 1 Nadika (24 minutes).
2 Nadika = 1 Muhurat (48 minutes)
30 Muhurat = 1 day (Hora = 24 hrs).
366 days = 1 solar year (12 solar months, 6 ritu, 2
Ayam i.e. Urayayan & Dakshinayam)
5 Solar yrs = 1 Yug.
The five solar yrs are also mentioned as Sanvatsar, Parivatsar, Idavatsar, Idvastar and Vatsar.
When the above five Savatsar have passed away, a yuga is over and the first solar year savatsar starts of the second Yuga. At this time Sun & Moon again come on the same Nakshatra in the Zodiac in sky.