"The Blitz", or heavy bombing of London by Germany in World War II, occurred over approximately how many days?

The London "Blitz" occurred in World War II between September 7th 1940 and May 21st 1941 or 267 days. London was targeted by the Germans 71 times, Birmingham, Liverpool and Plymouth 8 times, Bristol 6, Glasgow 5, Southampton 4, Portsmouth and Hull 3 and a minimum of one large raid on 8 other cities.

More than one million London houses were destroyed or damaged and more than 40,000 civilians were killed, almost half of them in London. Ports and industrial places outside London were also attacked. The main Atlantic sea port of Liverpool was bombed, causing nearly 4,000 deaths within the Mersey-side area during the war.

The bombing failed to demoralize the British into surrender or significantly damage the war economy. The eight months of bombing never seriously hampered British production and the war industries continued to operate and expand. The Blitz was only authorized when the Luftwaffe had failed to meet preconditions for a 1940 launch of Operation Sea Lion, the provisionally planned German invasion of Britain. By May 1941, the threat of an invasion of Britain had ended, and Hitler's attention turned to Operation Barbarossa, the invasion of the Soviet Union.