Why and when did The Beatles disband?

Answer 1

They disbanded officially in 1971, though the last time they ever played together publicly was on the roof of Abbey Road studios in January of 1969. Most if not all of them were married by that time, and all of them wanted to pursue solo careers (Paul McCartney had already released a solo album). Friction caused by the presence of Yoko Ono was another reason (though probably not the main reason, as some insist). And, ultimately, they were tired of it and wanted to get on with their individual lives.

Answer 2

In 1968 and 69, there were major arguments in the band - Ringo walked out in 1968, George in early 1969 although both were persuaded back. After recording Abbey Road, there was a brief recording session to finish I Me Mine from the Let It Be album (John Lennon did not attend). In September 1969, Lennon announced he was leaving the band to the other members but agreed to keep it quiet to help their business interests, in April 1970, Paul released a solo album (McCartney) and announced publicly that he was leaving the band. The Beatles legally disbanded in 1973, when their contract with EMI ended. There were rumours throughout the 1970s that the Beatles might reform, but they were obviously ended when Lennon was murdered in 1980. However, in 1996 the (then) three survivors reformed to record two "new" Beatle tracks - working with demo tracks recorded by John. For some years after the break-up, John, Paul, George and Ringo appeared to want to move on from their Beatle lives - but after the success of the Anthology project seemed to reconcile them to their past and Paul and Ringo will still call themselves Beatles.