India, Aug. 14 -- India and Pakistan mark their 80th Independence Day this week, 79 years since British rule ended - but not on the same date.

India observed it on August 15, 1947, when Independence formally took effect. Pakistan, born of the same act of Partition, celebrates a day earlier, on August 14, even though the documentary record shows both nations became free at the same moment.

Lord Louis Mountbatten, the last viceroy of India, signed off on the documents that created the two countries and partitioned Bengal and Punjab. He later said he settled on August 15 because it fell on the second anniversary of Japan's surrender in World War Two.

The Indian Independence Act, 1947, enacted towards the end of the British Raj, created th...