Earlier quoted context omitted.
> Very little is known of Mr. Balwani, including why he is called “Sunny.” This might be because Saturday in Hindi and other Indian languages is “sunny-var”, and the day of the week you are born on is a common nickname, in conjunction with “sunny” being an easy to pronounce and common English word.
This is absolutely incorrect. Saturday is called "Shani"-var (pronounced shunny) after the name for the Hindu god of justice [1]. Hindus also map his presence to the planet Saturn. Either way, no relation to the name Sunny at all. Source: several Indian friends of ages 18-50. 1: https://en.wikipedia.org/wiki/Shani
Sometime people named Sunil, such as the cricketer Sunil Gavaskar, use Sunny as a nickname.