I 'VE GOT THE FOLLOWING DATA ON CALCULATION OF PERIODS AS AVAILABLE IN THE "VEDAS":
YUGAMS - Krutha yugam - 17,28,000 years Thredha yugam - 12,96,000 years Dwapara yugam - 8,64,000 years Kali yugam - 4,32,000 years ----------- Total 43,20,000 years ---------------- These 43,20,000 years - 1 Sathur yugam or 1 Maha yugam Further it goes like this - 71 Sathur yugams are 1 Manvandhram 18 Sathur yugam - 1 Manu Rajyam 74 Manu Rajyam - 1 Indra Rajyam 270 Indra Rajyam - Lord Brhma's 1 Day 30 Brahma's days x 12 - 1 Brahma year 100 Brahma years - 1 Brahma's end 360 Brahmas - 1 Pralayam 100 Pralayams - 1 Vishnu Karpam and it goes further.
I HOPE THIS MIGHT BE OF HELP IN THE DISCUSSION REGARDING RAMAYANA AND MAHABHARATA PERIODS ETC.