Measurement of Year
The small unit of time is a nimesha, fifteen nimeshas constitute one kashtha, thirty kashthas make a kala and thirty kalas are one kshana. There are six kshanas in one danda, two dandas in one muhurta and thirty muhurtas in one day. There are thrity days in a month and each month is divided into two pakshas of fifteen days each. Two months constitute a season (ritu) and three ritus constitute an ayana. There are thus six seasons and two ayanas in a year.
The two ayanas are known as uttarayana and dakshinayana. One year for humans is equivalent to one day for the gods. Uttarayana corresponds to day for the gods and dashinayana to night.
Twelve thousand years of the gods are known as a mahayauga. Each mahayuga is divided into four sub-periods of Satya yuga, Treta yuga, Dvapara yuga and Kali yuga.
Two thousand mahayugas are merely one day for Brahma. There are fourteen eras (manvantara) in each of Brahma’s days. Brahma’s nights are just as long and it is during Brahma’s night that the world is destroyed and flooded with water. Each of Brahma’s days is called a Kalpa.
A hundred years for Brahma are equivalent to a single day for Vishnu.