cont.
there are total of 14 Manus or the progenitors in one universal cycle or the 'Kalpa'. the time taken by the Kalpa or universal cycle is equal to one catastrophe or the 'Pralaya'.

                                            one Mahayug or the great era  =  4320000 earth years.

Now total of 71 mahayug is equal to one Manu-era;   71* 4320000  =  30672000 earth years (human years).

More of all there are 14 Manus in a Universal cycle, so   14 * 30672000  =  429408000 earth years.

                   So in this manner we see that the method of time calculation in ancient Hindu india was far mujch beyond than any other civilization and more often it is as much accurate as the modern day's scientific methodology.