Charles Manson Is Now Model Inmate But He Used to be a Terror

Charles Manson is now a model prisoner ... because wreaking havoc behind bars is apparently a young man's game.

Sources with the California Department of Corrections tell TMZ ... The soon-to-be 83-year-old murderer hasn't violated prison rules since February 29, 2016 when guards found him in possession of a cell phone. A big no-no.

Prison officials believe Manson's on a 20-month goody two-shoes streak simply because of old age and health complications.

But Manson has not always been a model prisoner ... far from it. TMZ's obtained Manson's rap sheet in prison ... and he's tested patience for decades. There are over 100 infractions that go back to 1972, including ...

October 1972 -- Refused to shave

July 1973 -- Assault on staff

January 1975 -- Spitting and threatening staff

June 1977 -- Striking an officer

July 1978 -- Assault on correctional officer

April 1983 -- Possession of marijuana

July 1985 -- Possession of a hacksaw blade

February 1993 -- Assault and battery on non-prisoner

July 1993 -- Possession of a stabbing instrument

April 1995 -- Trafficking narcotics

Sept. 1995 -- Threatening to kill a police officer

March 1999 -- Battery on an inmate with weapon

December 2003 -- Possession of a deadly weapon

June 2009 -- Possession of a wrist watch

June 2015 -- Refusal to provide urine sample