Dec. 22, 2008: Then-prime minister Stephen Harper announces Duffy's appointment to the Senate as a representative for Prince Edward Island. Duffy is sworn in the next month.
December 2012: Questions are raised about how much time Duffy spends at his declared primary residence in P.E.I., since he claims living expenses for his longtime Ottawa-area home.
Dec. 4, 2012: Duffy says he got an email from Nigel Wright, the prime minister's chief of staff, saying it appeared that Duffy's residence expenses complied with the rules.
Feb. 8, 2013: The Senate hires external auditing firm to review residence claims of Duffy and two other senators.
Feb. 22, 2013: Claiming confusion with the rules, Duffy pledges to pay back the expenses.
April 19, 2013: Duffy confirms he has repaid more than $90,000 in Senate housing expenses. “I have always said that I am a man of my word. In keeping with the commitment I made to Canadians, I can confirm that I repaid these expenses in March 2013.”
May 12, 2013: The RCMP says it will examine Senate expense claims.
May 15, 2013: The PMO confirms a media report that Wright personally footed the bill for Duffy's housing expenses because Duffy couldn't make a timely payment.
May 28, 2013: Senate internal economy committee holds a public meeting to review Duffy's travel expenses. Senate finance officials say they've detected a pattern that concerns them. The committee votes to send the matter to the RCMP.
June 13, 2013: The RCMP confirms it has launched a formal investigation into Wright's involvement in the expense scandal.
Oct. 17, 2013: Claude Carignan, the government's new leader in the Senate, introduces motions to suspend Duffy, Sen. Pamela Wallin and Sen. Patrick Brazeau from the Senate over questioned expenses. The motions call for the three to be stripped of their pay, benefits and Senate resources.
Oct. 22, 2013: In an explosive speech in the Senate, Duffy accuses Harper's office of orchestrating a ”monstrous fraud” aimed at snuffing out controversy over his expenses. Duffy accuses the prime minister of being more interested in appeasing his Conservative base than the truth.
Nov. 5, 2013: Senators vote to suspend Brazeau, Duffy and Wallin without pay - but with health, dental and life insurance benefits intact - for the remainder of the parliamentary session.
July 17, 2014: Duffy is charged with 31 counts of fraud, breach of trust and bribery.
Sept. 23, 2014: A trial date is set for April 7, 2015, with 41 days set aside in April, May and June.
April 7, 2015: The trial begins with Duffy formally pleading not guilty to all charges. Deputy Crown attorney Mark Holmes says Duffy billed the Senate for thousands in “secondary residence” expenses though he did not live in Prince Edward Island and was just “commuting” from his Ottawa home. Holmes also says Duffy claimed travel payments for Senate business when he was attending family events. Defence lawyer Donald Bayne says Duffy operated within the often-fuzzy Senate rules.
May 14, 2015: The Senate appoints Ian Binnie, a retired Supreme Court of Canadian justice, as a special arbitrator for questioned expenses.
June 4, 2015: Auditor general Michael Ferguson releases an audit which flags a number of senators for questionable expenses.
Aug. 2, 2015: Harper calls a federal election. With the dissolution of Parliament for the Oct. 19 election, Senate suspensions for Duffy, Wallin and Brazeau are no longer in force.
Aug 21, 2015: Twitter says the Duffy trial is becoming the most tweeted-about election topic.
Aug. 26, 2015: Trial adjourns to November.
Oct. 19, 2015: Trudeau and the Liberals win a majority government, Harper quits as Conservative leader.
Dec. 8, 2015: Duffy takes the stand for six days of testimony and two days of cross-examination.
March 21, 2016: Binnie releases his report. He says in 10 of 14 cases of questioned expenses, he reduced the total. He says he imputed no bad motives to any of the senators.
April 21, 2016: Duffy is acquitted on all counts.
May 2, 2016; Duffy returns to Parliament Hill
July 25, 2016: The Senate says it will claw back $17,000 in expenses from Duffy.
Aug. 24, 2017: Duffy announces he is suing both the Senate and the government of Canada over the actions of the RCMP.