What is "shashanka"

Shashanka, a Brahmin is often attributed with creating the first separate political entity in a unified Bengal, called the Gauda Kingdom and as such is a major figure in Bengali history. He reigned in 7th century AD, and some historians place his rule approximately between 590 AD and 625 AD. He is the contemporary of Harsha and of Bhaskar Varman of Kamarupa. His capital was at Karnasuvarna, in present-day Murshidabad. The development of the Bengali calendar is often attributed to Shashanka because the starting date falls within his reign.