Two business tycoons of Indian industry (20th and early 21st century) Dhirubhai Ambani and Ratan Tata share a common birth date – December 28. The late Dhirajlal Hirachand Ambani, popularly known as Dhirubhai, was born on December 28, 1932. Dhirubhai was an Indian rags-to-riches business tycoon who early in his career founded Reliance Industries in Mumbai. December 28 marks an important day in the Ambani family calendar, with the family having announced major milestones from time to time in memory of the late patriarch. Former Tata Sons Chairman Ratan Tata was also born on December 28, 1937, in Mumbai to Naval Tata and Sooni Tata. He turned 85 today. Ratan Tata became the chairman of the Tata Group in 1991.