I am having a doubt about the calendars and date calculation.
We know the calendar which we use now is the Greogorian Calendar which was introduced to India after the Europeans came to India. Before that, Indians traditional date system is that 12 months (chithirai, vaikasi..) and the 60 years in the tamil calendar. This 60 years with the respective names will be repeated and they didn't had the incremental numbers on its own.
If this is so, how do we calculate the lifetime period of the Chola kings ? Or if the kalvettus and inscriptions that we get contain the Gregorian calendar years like 985 AD etc ? Or the inscriptions contain the old tamil year names ?
Or is it only the carbon dating (or any similar mechanism) used to find the age of the kalvettus ?
We have "Thiruvalluvar" Year and "Kali" year. You can find this on any Tamil daily sheet calender. I think all stone inscriptions are based on the Kali year.
Interestingly, KNS discusses the same issue in the first chapter in the 'A brief history of south India' and explains the various ways of dating the kalvettus. Saka era dating is common in some kalvettus and others are dated by their language (usage of words, whether vatteluthu was used etc, this is extensively used by Vaiyapuri pillai for dating the sangam era literature). Also, mentioning of celestial events also help in dating the inscriptions. Since the book is written in 1955, I assume that carbon dating was not in vogue at that time!!
Not sure about Kali year but I think Thiruvalluvar year is a recent invention and not used in kalvettus..