U.S. special counsel Robert Mueller’s office recommended that Michael Flynn, President Donald Trump’s short-lived national security adviser, serve no prison time for lying to the FBI about his contacts with Russian officials.

Flynn pleaded guilty a year ago this week and is set to be sentenced on Dec. 18 at the U.S. District Court for the District of Columbia.

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Flynn’s crime of lying to the FBI carries a maximum sentence of five years in prison. Under the plea agreement he signed, Flynn can receive a sentence from between zero and six months.

He can also request that he pay no fine.

According to the special counsel’s recommendation, Flynn has been cooperating with the investigation into Russian interferrence in the 2016 election.

Flynn resigned on Feb. 17, 2017, just 24 days into his term as national security adviser, after he was found to have lied to Vice President Mike Pence about discussions he had with Russia’s then-ambassador to the U.S., Sergey Kislyak.

In his plea agreement, Flynn admitted he also lied to the FBI about conversations he had with Kislyak over U.S. sanctions against Russia in the days before Trump was sworn in as president.

Flynn is the only member the Trump administration to plead guilty to a crime uncovered by Mueller’s team during the investigation into Russian attempts to influence the 2016 U.S. presidential election.

He is the fourth member Trump’s campaign to be charged with a felony.

On Oct. 30, 2017, Mueller announced indictments against former Trump campaign chairman Paul Manafort and associate Rick Gates on charges of conspiracy against the United States, being an unregistered foreign agent, money laundering and failing to file reports of foreign bank and financial accounts.

Earlier that month, campaign volunteer George Papadopoulos pleaded guilty to lying to the FBI as part of a cooperation agreement with Mueller.

Here’s a timeline of events of Flynn’s tenure as national security adviser and beyond:

Nov. 18, 2016 – Trump announces that Flynn has been offered the post of national security adviser. Flynn accepts the job.

Dec. 28, 2016 – Flynn and Sergey Kislyak, the Russian ambassador to the United States, exchange Christmas text messages by cellphone.

Dec. 29, 2016 – President Barack Obama announces sanctions against Russia for alleged interference in the 2016 presidential election. He orders 35 Russian diplomats out of the country.

Dec. 29, 2016 – On the same day, Flynn calls the Russian ambassador. The New York Times reports that Flynn, according to officials who saw a transcript of the wiretapped conversation between Flynn and Kislyak, discussed the sanctions that the Obama administration had imposed on Russia.

Jan. 13, 2017 – The Wall Street Journal reports, for the first time, Flynn's talks with the Russian ambassador.

Jan. 14, 2017 – According to Pence, Flynn tells him that he and Kislyak did not talk about Russian sanctions.

Jan. 15, 2017 – Pence appears on "Fox News Sunday" and says that Flynn's conversations with the Russian ambassador "were not in any way related to the new U.S. sanctions against Russia or the expulsion of diplomats."

Jan. 20, 2017 – Trump is sworn in as the 45th president of the United States.

Jan. 22, 2017 – The Wall Street Journal reports that Flynn is under investigation by U.S. counterintelligence for the phone calls to the Russian ambassador.

Late January: Acting Attorney General Sally Yates informs the White House counsel of Flynn's misleading statements.

Feb. 8, 2017 – Flynn, in an interview with the Washington Post, denies discussing sanctions with the Russian ambassador.

Feb. 9, 2017 -- Flynn's spokesman tells the Washington Post that Flynn "indicated that while he had no recollection of discussing sanctions, he couldn't be certain that the topic never came up."

Feb. 10, 2017 – Trump, on the way to Mar-a-Lago, tells reporters aboard Air Force One he had not seen the reports about Flynn. "I don't know about that," he says. "I haven't seen it."

Feb. 11/12, 2017 – Flynn stays the weekend at Mar-a-Lago.

Feb. 12, 2017 – Pence says on CBS that he spoke to Flynn about the phone call and the conversation had "nothing whatsoever to do with those sanctions."

Feb. 13, 2017 – White House adviser Kellyanne Conway says around 5 p.m. that the administration has "full confidence" in Flynn. Minutes later, Sean Spicer, press spokesman for the White House, issues a statement that reads: "The president is evaluating the situation. He's speaking to the vice president relative to the conversation the vice president had with Gen. Flynn, and also speaking to various other people about what he considers the single most important subject there is: our national security." The Washington Post reports at 8 p.m.  that the Justice Department told White House officials that Flynn "mischaracterized his communications."

Feb. 13, 2017 – Flynn resigns his position of national security adviser just before 11 p.m.

“Unfortunately, because of the fast pace of events, I inadvertently briefed the vice president-elect and others with incomplete information regarding my phone calls with the Russian ambassador,” Flynn wrote in his resignation letter. “I have sincerely apologized to the president and the vice president, and they have accepted my apology.

“I am tendering my resignation, honored to have served our nation and the American people in such a distinguished way."

Feb. 13, 2017 – Lt. Gen. Joseph K. Kellogg Jr. is named acting national security adviser just after 11 p.m.

Feb. 20, 2017 – Gen. H.R. McMaster is sworn in as national security adviser.

Oct. 5, 2017 – Papadopoulos pleads guilty to lying to the FBI as part of a cooperation agreement with Mueller.

Oct. 30, 2017 – Mueller's office indicts Manafort and associate Gates on charges of conspiracy against the United States, being an unregistered foreign agent, money laundering, and seven counts of failing to file reports of foreign bank and financial accounts.

Dec. 1, 2017 – Flynn is indicted on charges he lied to the FBI. He pleaded guilty to the charges.

Dec. 15, 2017 – Trump does not rule out a pardon or Flynn, but tells a reporter, "I don't want to talk about pardons for Michael Flynn yet. We'll see what happens. Let's see. I can say this, when you look at what's gone on with the FBI and with the Justice Department, people are very, very angry." 

April 23, 2018 – Flynn's son, Michael Flynn Jr., tweets that his father did not lie to

Pence about calling Kislyak, and in a second tweet suggests that the two men could have had a “misunderstanding.”

Sources: New York Times; Washington Post; BBC, The Associated Press