Siva Puran says “Lord Shiva informed us that my day consists of four thousand eras and similarly my night too consists of four

thousand eras. Since a month consists of thirty days and a year consists of twelve months. In this way my age

was fixed to be of one hundred years. One day of Vishnu is equivalent to one year of Brahma. Vishnu’s age too

was fixed to be of one hundred years. The day of Rudra is equivalent to one year of Vishnu and his age also was

fixed to be of one hundred years.”