Tamil literature is very clear in saying that the main task of the short and smart ascetics is to prevent human beings from being scorched. So they absorb the excess heat from the sun by travelling in front of him. Tamil books also add they were in turn given energy by Lord Skanda and Goddess Durga.
For this, I took my grandfather Professor. Geometry Narayana Iyer's words, for if a grandson does not belive a grandfather, who else would? I think my grandfather would be happy, wherever he is now. The Aitreya Shiksha is in Germany and to the surprise of many it is in ancient Tamil ! This also proves my Theory that Sanatana Dharma was in place in the South, probably even before the Sarasvati Valley!
This makes it difficult to date them precisely as they have lived at different points of time. Shankaracharya' Guru Govinda Bhagavadpada, one study claims lived during the period of Vikramaditya as there are two Vikramadityas,one of the Maurya and another of the Chalukya dynasty. The first one lived around 4th Century CE, while the latter in (Vikramaditya II )(733–746 CE) 2.The internal evidence of Shankaracharya's works do not provide many a clue,exception being the one about Thirugnana Sambhandar, who, it is agreed, is addressed by Shankaracharya as 'Dravida Sisu' in his Sounday
I have misplaced it. I shall find and update. Meanwhile The following is a list from the web