Context: Richard John Cyril "Rick" Allen (born 1 November 1963) is an English drummer who has played for the hard rock band Def Leppard since 1978. He overcame the amputation of his left arm in 1985 and continued to play with the band, which subsequently went on to its most commercially successful phase. He is known as "The Thunder God" by fans.

Question: what year did the drummer lose his arm?
Steam of consciousness below:
To answer this question, we should know that: He overcame the amputation of his left arm in 1985 and continued to play with the band, which subsequently went on to its most commercially successful phase.
So, the answer is 1985.