Here is one source from a fictional account confirming midnight of August 15th, 1947 (Bombay local time), Salman Rushdie's Midnight Children:
I was born in the city of Bombay ... once upon a time. No, that won't
do, there's no getting away from the date: I was born in Doctor
Narlikar's Nursing Home on August 15th, 1947. And the time? The time
matters, too. Well then: at night. No, it's important to be more ...
On the stroke of midnight, as a matter of fact. Clock-hands joined
palms in respectful greeting as I came. Oh, spell it out, spell it
out: at the precise instant of India's arrival at independence I
tumbled forth into the world.