The 39-year-old actor was sentenced to four months in the Ozaukee County Jail last June, after being charged with carrying a concealed weapon and disorderly conduct following a barroom brawl in which Diamond stabbed another man.
“I sincerely apologize to everyone involved,” the former Saved by the Bell star said at the time of his sentencing. “This was the single most terrifying experience of my life … This is all I’ve been able to think about for the last six months.”
Last month, he dropped his appeal of the disorderly conduct conviction and agreed to start serving his sentence, which includes work release, on Jan. 15.
While he was convicted of the two lesser misdemeanors, Diamond was found not guilty of the more serious felony charge of recklessly endangering public safety.
“I’ve got to say I’m really proud of him,” Diamond’s attorney Thomas Alberti told PEOPLE in June. “He gets it. I think he did the best that he could in the moment that he had to make the decision, but he certainly understands that you don’t want to send the message to society that it should be the Wild West in a bar scene.”