Darren Haynes, of The Official UK Charts Company, said: "These days, barcodes and computers are used but, in 1971, record shops had to fill in 'diaries' of all sales and send them by post to the chart compiler.
"For those weeks in 1971, the strike resulted in no official album charts being included in Record Retailer, the official music business chart magazine.
"Historians let the last valid chart run across the missing weeks, meaning Simon and Garfunkel were given another eight weeks at the top but now All Things Must Pass has taken its rightful place as a No 1 record for the full eight-week period."
George's widow, Olivia, said: " He'd love that it reached No 1 in the country in which he lived."
The entry has now been changed in the official Guinness Book of British Hit Singles and Albums.