Dear Alakendu Das,
Generally, Dharmakīrti is thought to flourish between 600-660, however I’d refer you to my paper
“On the Relative Chronology of Dharmakīrti and Samantabhadra,” Journal of Indian Philosophy 42 (2014) 1-47, available here: www.balcerowicz.eu/indology/balcerowicz2014b.pdf
It provides (perhaps the most up-to-date) review of his dates and new dating based on additional, non-Buddhist references.
Best regards,
Piotr Balcerowicz