Brahma and Time

I think the universe will end some day, I will end much sooner, I will get mixed in the soil, air, water and space. The universe is part of the cycle of formation and destruction then formation and so on. The Big Bang is described as the birth of the universe (Brahma), the life of the universe then follows (Vishnu), and the Big Crunch would be described as the destruction of the universe (Shiva).

sahasra-yuga-paryantam
ahar yad brahmano viduh
ratrim yuga-sahasrantam
te 'ho-ratra-vido janah

By human calculation, thousand ages taken together form the duration of Brahma's one day. And such also is the duration of his night. (Bhagvad Gita)
During Brahma’s one day known as Kalpa four yuga cycle is completed. Satya yuga, Treta Yuga, Dvapar yuga and Kal yuga. Kal yuga is the period we are living in today and we have complete 5000 years of kal yuga, it is suppose to be 432,000 years, long way to go.

Can Brahma’s one day could be so long. Consider bacteria, these bacteria’s live less than few hours. When compared with human day many generations of bacteria pass by in a single human day. In that time period that bacteria will grow, mate, die (they don’t have time to waste). I look like Brahma to these bacteria, as I give them chance to grow on or in me, nourish them, and then destroy by some antibacterial. The cycle will continue. This is how Brahma days look like in lay mans term. Look at Mayfly it just lives day or two. Mayfly goes through the whole life cycle in two days, while I was still deciding on the X-Box deal.

Who decide how long the day should be. Sunset-sunrise seems to be nice one. Consider one moon cycle to be day and other moon cycle to be night, (Krishna paksh and Shukla paksh) 15 days each, we can have one day as compared to 30 days and 12 days in whole year. Average life expectancy will be not more than 2.5 years.