I know there are already some really detailed time-lines floating around, but I have some trouble with them, because they don’t really tend to explain the source of information and seem to consist of a lot of guesswork (which is fine, I just would like to know what kind of guesswork). I am also not a fan of the practice to assume that something happened exactly on the release date of a movie. So I did my own one and tried to explain as precise as possible how I came up with the timeline.
With one or two exceptions I did not use the tie-in comics as source, because they often contradict the movies. I did included Agents of SHIELD and the Marvel Shorts, though. Otherwise the only supplanting material I used is the official Marvel Timeline (which I mostly used to figure out how Iron Man 2, The Incredible Hulk and Thor 1 line up), the memorabilia documents, provided that they didn’t contradict anything (usually, they did) and WHIH promotion material. For the movies, I tried to do a day-to-day listing if possible, but it is sometimes difficult to do so for Agent of SHIELD, because not only are the characters often in-doors, the show is also constantly jumping around between different time zones, it is not even revealed were the various bases are actually located, plus we have no idea how fast they can travel. Generally I tried to keep it as brief as possible. This is about the general order of events, for further details about the characters, there is a really comprehensive wikia for the MCU.
There are three kinds of sources. “Confirmed” means that the date in question was clearly given in the movie. Those are non-negotiable. “Dialogue”, “Voiceover” or similar means that the date is based on something mentioned in the movie. Those dates I usually take as a given, unless they contradict something which has already been established. Props I included only if they fit into the time-line, and I added my reasoning for including or leaving the information in them out. I left out most of the memorabilia information out, because it usually contradicts the time-line, but remarked on the ones which do fit more or less. There are a few dates on props which are repeated that often in multiple movies, that I consider them canon. I also used some historical dates as a baseline. I don't use release dates as a source. Everything is strictly based on information which are mentioned in-universe.
I used abbreviations for the sources, following a simple system: The movies start with an abbreviation for the franchise (usually two letters) plus an indication which movie of the franchise it is (Ant-man is the exception since the second one is supposed to be called Ant-man and the Wasp either way):
Ironman = IM:1
Ironman 2 = IM:2
Ironman 3 = IM:3
Thor = TH:1
Thor, The Dark World = TH:TDW
The Incredible Hulk = IH:1
Captain America, The First Avenger = CA:TFA
Captain America, The Winter Solder = CA:TWS
The Avengers = TA:1
The Avengers, Age of Ultron = TA:AoU
Guardians of the Galaxy = GotG:1
Ant-man = AM
The One Shots all start with OS and then an abbreviation for the Title (I went short for a very long one, though)
Agent Carter = OS:AC
The Consultant = OS:TC
A Funny Thing Happened on the Way to Thor's Hammer = OS:AFT
Item 47 = OS:I47
All Hail the King = OS: AHTK
The TV Shows start with an abbreviation of the title, followed by the season and then the episode of the season. AC:1,07 for example means the seventh episode of Agent Carter, AoS:2,11 mean the eleventh episode of the second season of Agents of SHIELD.
Agents of S.H.I.E.L.D. = AoS
Agent Carter = AC
Marvel's most wanted = MMW
Damage Control = DC
Daredevil = DD
Jessica Jones = JJ
Luke Cage = LC
Iron Fist = IF
The Defenders = TD
A couple of times I noted that dates are from WHIH or the Memorabilia files. In this case I am talking about promotional material which I took into account whenever I felt that it was adding something to the timeline without contradicting anything.
One of the biggest changes I did compared to other time-lines is that I decided to set The Winter Soldier in fall 2013 instead of spring 2014. I am aware that at one point in phase 2 the MCU started to release the movies in real time. But Agents of S.H.I.E.L.D. was at least initially half a year behind, at least until season 3 in which it seems they started to think in real time, too. I nevertheless tried to connect the dates as well as possible.
Feel free to comment on dates I have overlooked, or challenge my reasoning. I intend to update the timeline from time to time.