Question: When was the  Brāhmasphuṭasiddhānta written??
Answer:
When was the  Brāhmasphuṭasiddhānta written?
The Brāhmasphuṭasiddhānta ("Correctly Established Doctrine of Brahma", abbreviated BSS)
is the main work of Brahmagupta, written c. 628.[1] Τhis text of mathematical astronomy contains significant mathematical content, including a good understanding of the role of zero, rules for manipulating both negative and positive numbers, a method for computing square roots, methods of solving linear and quadratic equations, and rules for summing series, Brahmagupta's identity,  and  Brahmagupta’s theorem. 
c. 628