Do you know why British left India on 15th August?

 I mean why this specific date? Why 15th August?

The reason was this man

The man is

His Excellency Rear Admiral the Right Honourable Lord Louis Francis Albert Victor Nicholas, Viscount Mountbatten of Burma, KCG, PC GMSI, GCFO, KCB, DSO, the outgoing Supreme Allied Commander in South East Asia.

In short,

Lord Mountbatten.

Last viceroy and first governor general of India.

He was a very pompous and proud man. He was the Commander of Allied forces in South east Asia in 1945. It was him before whom, Japan surrendered after atomic attacks on 6th and 9th August.

The date of surrender was 15th August. Lord Mountbatten took extreme pride in this achievement and considered this date as his lucky day.

Therefore he decided to grant India freedom on this particular day.

 Why India got freedom in midnight of 15th August? Why midnight (12:00 am, 15th August)

Reason was superstition.

Indian astrologers, based on their calculations, strongly believed that 15 August is an inauspicious day. But Mountbatten was adamant for 15th August. A compromise was sought out.

Midnight of 15 will be still 14th August because in Indian system, a new day begins with sunrise, while it will be 15th August for British because new day starts at midnight in British system.

Everybody was happy. :)