Little bit of specific timeline info for Civil War.
At beginning, during scene where Wanda is being talked through scoping out surrounding area while sitting and drinking tea/coffee, there's a newspaper on her table with a picture of Crossbones/Rumlow, with headline "Police Stations Robbed" under his picture.
The newspaper is "The Daily", and its the Saturday edition. The top portion is out of focus so no specific date is visible on newspaper, but it does feature a blurb on bottom that reads "2016 Election Conversations, Sunday, March 22, 3-5 PM. Be Part of the Audience."
That would seem to indicate (if the paper is meant to be that day's issue) the modern day portions of Civil War begin on Saturday, March 21, 2016. Of course in reality March 21, 2016 was a Monday, so this is another example where the MCU timeline (in terms of day of week matching up to dates) differs from reality.
It's also entirely possible the newspaper is a bit old (few weeks or months) and Wanda just had it as dossier material, since they were actively looking for Rumlow.
However there is a second newspaper next to the first one, called The Spot (also with a Saturday label) with headline "Weapons Sold to Terrorists", also featuring a picture of Rumlow.
So, if I had to guess, the opening scenes in Lagos happen on March 21, 2016. Presumably the rest of film occurs in late April, with the WHIH promos occurring in early March before events in Lagos, and final one occurring that night (reporting on the Lagos explosion).
Also, the final scene with Tony helping Rhodey try out the new harness to help him walk happens on April 14, 2016. The Fedex package (delivered by Stan Lee in his requisite cameo) is labeled as a 2 Day package, delivered on/by Tuesday, April 14 (April 14 in real world was a Thursday, so Marvel is keeping the habit of date/days not matching reality).
Therefore I can probably determine a precise timeline for the film down to days throughout.
Moved Age of Ultron up a month, so that Zemo's line "I've thought about nothing else for over a year", referring to the Battle of Sokovia and the death of Zemo's family, makes sense.
This is only preliminary until Bluray/DVD comes out and I can time code and double check, but I believe the dates work out like this:
March 21 - Prologue: Lagos Incident
Day 1 / April 5 - Tony's presentation at MIT
Day 2 / April 6 - Cap & Wanda see news report about Lagos, Ross presents Sokovia Accords to team
Day 5 / April 9 - Peggy's Funeral, Bombing at Sokovia Accords UN Assembly
Day 6 / April 10 - Cap finds Bucky in Romania, they're captured by authorities, Steve once again refuses to sign Accords, Zemo brainwashes Bucky and he escapes custody, Cap hides him from authorities, Tony recruits Peter Parker, Clint frees Wanda
Day 7 / April 11 - Battle at Leipzig Airport, Cap and Bucky follow Zemo to Siberia, Tony and Black Panther follow as well, battle between Cap, Tony, and Bucky; Zemo is captured
Day 8 / April 12 - Post-Credit Scene: Peter Parker nurses bruised eye, discovers Spider-signal in web launcher that Tony made for him
Day 10 / April 14 - Tony receives package from Cap, Cap breaks the imprisoned Avengers out of Raft
Day 11 / April 15 - Mid-Credit Scene: Bucky is put into suspended animation in Wakanda, Steve also hides out in Wakanda (presumably with the fugitive Avengers)
If we're thinking of the same line, I think he actually said said
four years.
You can hear the line at the beginning of this behind-the-scenes clip here. (I remember hearing it as four years when I saw the film as well.) I don't think there was a specific mention of SHIELD's fall, though, so it seems likely that Ross was actually referring to the first time the group came together in Avengers, which was technically on their own initiative. (This would line up with Avengers taking place in 2012.)
There are also definite references to the amount of time Steve and Falcon have been searching for Bucky without success (in the line to which Steve responds "We didn't blow up the UN") and how many years ago Tony blew up his suits in Iron Man 3 (in the pen/Pepper scene with Tony and Steve.) I
think these are both two years, which would weirdly correspond to the release date for Winter Soldier and the onscreen dates for Iron Man 3, but I couldn't remember by the end of both screenings. (It's a long movie!)
Civil War does seem to indicate that the rule that the movies take place in the year they were released trumps any time references on screen or in dialogue. (Though of course, it's only Civil War's dialogue that would indicate this!

)
TC
Think you're right. I thought it was 3 years but my buddy says he remembers it as four years as well. I'll have to watch it again. If it is four years, Ross is simply referring to the creation of the Avengers in 2012, it seems, which makes just as much sense.