"He (Iltutmish) also captured the city of Ujjain, and having destroyed the idol-temple of Ujjain which had been built six hundred years previously, and was callled Mahakal, he levelled it to its foundations, and threw down the image... from whom the Hindus reckon their era."
January 1, 1970
https://en.wikiquote.org/wiki/Ujjain