Shaykh Zafar ud Deen al Bihāri al Hanafi, may Allah have mercy upon him, (1303-1382 hijri) was one of the great scholars in the Indian Sub-continent at the turn of the century. He had been given the title 'Malik ul ulama' by his contemporaries meaning they deemed him the king amongst the ulama of his time. He was not just a great muhaddith and jurist but was also a master of Science and worldly knowledge. In particular he was renowned for establishing accurate salah times for different areas using his expertise in both fiqh and science. He was also a prolific writer and debater.
Abridged biography courtesy Muhammad Sajid Younus in Benefitting the Deceased: The Good Practices of the Prophet ﷺ and His Companions