By Arden Farhi, Margaret Brennan, Louise Dufresne, Josh Gross, Kathryn Watson and Jacqueline Alemany. This timeline was originally published on Feb. 14, 2017.

Dec. 10, 2015: Michael Flynn travels to Russia; meets with President Vladimir Putin

Nov. 9, 2016: Donald Trump wins presidential election

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(The election, of course, was Nov. 8, but he wasn't officially declared the victor until early Nov. 9.)

Nov. 17, 2016: President-elect Trump offers Flynn White House post as national security adviser

Nov. 18, 2016: Flynn accepts position

Dec. 4, 2016: Flynn's son Michael Flynn Jr., a transition staffer, tweets on #Pizzagate

@MFlynnJr: Until #Pizzagate proven to be false, it'll remain a story. The left seems to forget #PodestaEmails and the many "coincidences" tied to it.

#Pizzagate is a thoroughly debunked conspiracy theory involving Hillary Clinton and a Washington, D.C. pizzeria.

Dec. 6, 2016: Flynn's son, Michael Flynn Jr. is forced to resign from Trump transition team over #pizzagate

Dec. 12, 2016: U.S. official confirms U.S. has "high confidence" Russian intelligence agency GRU hacked the DNC and DCCC

In October, the U.S. intelligence community concluded that Russia was behind the cyberattacks.

Dec. 22, 2016: Jared Kushner, CBS News confirmed at a later date, instructs Flynn to contact the Russian government on U.N. Security Council resolution on Israeli settlements. Flynn reaches out to Russian Ambassador to the U.S. Sergey Kislyak.

Dec. 25, 2016 (Christmas): Flynn texts Kislyak

Flynn reached out to wish the ambassador a merry Christmas and the ambassador returned those greetings. Flynn offered his condolences for the loss of 92 members of a Russian military choir killed in a plane crash.

Dec. 28, 2016: Obama signs executive order imposing new sanctions on Russia to take effect the next day

Dec. 28, 2016: Kislyak reaches out to Flynn

Kislyak reached out to Flynn to discuss logistics of setting up a phone call between Trump and Putin to take place after Inauguration Day, according to Spicer's Jan. 13 briefing.

Dec. 29, 2016: K.T. McFarland, according to later CBS confirmation, while at Mar-a-Lago and with other top officials including Reince Priebus, Kellyanne Conway, Stephen Miller and Steve Bannon, tells Flynn to communicate to Kislyak about the U.S. sanctions. Flynn calls Kislyak.

Dec. 29. 2016: Russian sanctions announced

Obama administration announces sanctions on Russia for the cyber attack; 35 Russian diplomats expelled; two Russian diplomatic facilities in the U.S. shuttered.

President-elect Trump's reaction: "It's time for our country to move on to bigger and better things. Nevertheless, in the interest of our country and its great people, I will meet with leaders of the intelligence community next week in order to be updated on the facts of this situation."

Dec. 30, 2016: Trump tweets about Putin's "great move"

Great move on delay (by V. Putin) - I always knew he was very smart! — Donald J. Trump (@realDonaldTrump) December 30, 2016

Jan. 12, 2017: Washington Post's David Ignatius first reports Flynn and Russian ambassador spoke by phone

Jan. 13, 2017: Reuters reports there were five phone calls between Flynn and the Russian ambassador on the day the U.S. announced retaliatory sanctions.

Jan. 15, 2017 Mike Pence appears on "Face the Nation" and defends Flynn

JOHN DICKERSON: Let me ask you about it was reported by David Ignatius that the incoming national security advisor Michael Flynn was in touch with the Russian ambassador on the day the United States government announced sanctions for Russian interference with the election. Did that contact help with that Russian kind of moderate response to it? That there was no counter-reaction from Russia. Did the Flynn conversation help pave the way for that sort of more temperate Russian response? MIKE PENCE: I talked to General Flynn about that conversation and actually was initiated on Christmas Day he had sent a text to the Russian ambassador to express not only Christmas wishes but sympathy for the loss of life in the airplane crash that took place. It was strictly coincidental that they had a conversation. They did not discuss anything having to do with the United States' decision to expel diplomats or impose censure against Russia. JOHN DICKERSON: So did they ever have a conversation about sanctions ever on those days or any other day? MIKE PENCE: They did not have a discussion contemporaneous with U.S. actions on-- JOHN DICKERSON: But what about after-- MIKE PENCE: --my conversation with General Flynn. Well, look. General Flynn has been in touch with diplomatic leaders, security leaders in some 30 countries. That's exactly what the incoming national security advisor-- JOHN DICKERSON: Absolutely. MIKE PENCE: --should do. But what I can confirm, having spoken to him about it, is that those conversations that happened to occur around the time that the United States took action to expel diplomats had nothing whatsoever to do with those sanctions. JOHN DICKERSON: But that still leaves open the possibility that there might have been other conversations about the sanctions. MIKE PENCE: I don't believe there were more conversations. JOHN DICKERSON: Okay. Okay. Okay. That's all I want. Okay. Got it-- MIKE PENCE: --confirm that those elements were not part of that discussion.

Jan. 20, 2017 Inauguration Day: Trump sworn in as the 45th president

Jan. 22, 2017 Michael Flynn sworn in as national security adviser

Jan. 23, 2017 Sean Spicer on contacts between Flynn and Russian ambassador

White House confirms two calls between Flynn and Kislyak.

QUESTION: Were those conversations about anything else other than setting up that discussion? And why has that discussion not yet happened between the president and President Putin? SPICER: So there's been one call. I talked to General Flynn about this again last night. One call, talked about four subjects. One was the loss of life that occurred in the plane crash that took their military choir, two was Christmas and holiday greetings, three was to -- to talk about a conference in Syria on ISIS and four was to set up a -- to talk about after the inauguration setting up a call between President Putin and President Trump. That -- I don't believe that that has been set up yet because the call was to say -- they did follow up, I'm sorry, two days ago about how to facilitate that call once again. So there have been a total of two calls with the ambassador and General Flynn. And the second call came -- I think it's now three days ago -- that was to say once he gets into office, can we set up that call? It hasn't -- to my knowledge, has not occurred yet.

Jan. 24, 2017 Flynn is interviewed by the FBI, and lies in the process

According to prosecutors in court documents released months later, Flynn lied to the FBI about his contacts with Kislyak.

Jan. 26, 2017 Department of Justice informs White House that Flynn may have misled administration officials

DOJ officials inform the White House Office of Legal Counsel that Flynn may have misled senior administration officials about the nature of his communications with Russian ambassador. Mr. Trump was briefed.

Jan. 27, 2017 Trump and Comey have dinner; Trump, according to Comey, demands loyalty pledge

Jan. 28, 2017 - Trump speaks with Putin

White House readout:

"President Donald J. Trump received a congratulatory call today from Russian President Vladimir Putin. The call lasted approximately one hour and ranged in topics from mutual cooperation in defeating ISIS to efforts in working together to achieve more peace throughout the world including Syria. The positive call was a significant start to improving the relationship between the United States and Russia that is in need of repair. Both President Trump and President Putin are hopeful that after today's call the two sides can move quickly to tackle terrorism and other important issues of mutual concern."

Feb. 1, 2017 Flynn says Iran is "on notice"

In an appearance in the White House briefing room, Flynn said, "As of today we are officially putting Iran on notice."

Feb. 9, 2017 Pence learns that Flynn lied to him about conversations with Kislyak

Feb. 10, 2017 Flynn spokesman claims Flynn can't be certain if sanctions were discussed

The Washington Post reports that Flynn doesn't recall but cannot be 100 percent certain whether Russia sanctions came up during his phone conversation with the Russian ambassador to the U.S. The report cited a White House official who had spoken to him. Flynn said he doesn't remember any part of the discussion involving sanctions. When asked about possible transcripts of phone conversations that would have been intercepted by U.S. intelligence agencies who may have been monitoring the calls, the official said he hadn't seen them and had no comment.

Feb. 10, 2017 Aboard Air Force One, Trump denies knowledge of Flynn's conversations with ambassador

QUESTION: Mr. President what do you make of reports that General Flynn had conversations with the Russians about sanctions before you were sworn in? POTUS: I don't know about it. I haven't seen it. What report is that? POTUS: I haven't seen that. I'll look at that.

When asked how the cable news-loving president was unaware of the Flynn matter, the White House told Margaret Brennan "he had a full day."

Feb. 13, 2017: White House mixes messages, expressing full confidence in Flynn, then saying it is reviewing the situation

Flynn participates in calls with leaders from South Africa and Nigeria. He also appears in the front row of a press conference with Canadian Prime Minister Justin Trudeau.

Kellyanne Conway says Flynn "does enjoy the full confidence of the president."

An hour later, the White House released a statement saying, "The President is evaluating the situation..."

Feb. 13, 2017: Flynn resigns; Keith Kellogg named interim national security adviser

Flynn submits resignation letter to the president, says "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."

Feb. 14, 2017: Kremlin calls Flynn's ouster an "internal matter"

"This is the internal business of the Americans, it is the internal business of President Trump's administration. This is not our business," Kremlin spokesman Dmitry Peskov told journalists.

Feb. 15, 2017: Trump calls Flynn a "wonderful man" in joint presser with Israeli Prime Minister Benjamin Netanyahu

March 31, 2017: Trump tweets Flynn should ask for immunity

"Mike Flynn should ask for immunity in that this is a witch hunt (excuse for big election loss), by media & Dems, of historic proportion!" the president tweeted.

Dec. 1, 2017: Flynn pleads guilty to lying to the FBI

Flynn pleads guilty to one count of lying to the FBI and states he is cooperating with Special Counsel Robert Mueller's investigation into Russian meddling.

Dec. 2, 2017: Trump says he fired Flynn because he lied to Pence and the FBI

Mr. Trump takes to Twitter, saying he fired Flynn because he lied to Pence and the FBI, raising questions about whether Mr. Trump did indeed know Flynn lied to the FBI at the time Flynn was ousted. If he did know Flynn lied to the FBI at the time, then his reported request to Comey on Feb. 14, one day after Flynn's firing, to drop the Flynn matter becomes increasingly interesting for Mueller.

"I had to fire General Flynn because he lied to the Vice President and the FBI. He has pled guilty to those lies. It is a shame because his actions during the transition were lawful. There was nothing to hide!" Mr. Trump tweeted.