Is it ever made clear officially what the timeline of the Marvel Cinematic Universe is and where Agents of S.H.I.E.L.D falls on it?
Pulling from the The Comic Board Forum (and IM3 in movie references):
- December 31, 1999, Tony Stark learns about Extremis from Maya Hansen (Beginning of IM3)
- 2008, Tony Stark demonstrates the Jericho outside of Kabul, Afghanistan. (exact date unsure - Beginning of IM1)
- May 5, 2012, Battle of New York. (Avengers)
- December 27, 2012, With Stark's help, Potts' Extremis effects are stabilized. (End of IM3)
- September 24, 2013, Agents Fitz and Simmons discover the explosion which occurs was from a person, as well as that it comes from the Extremis within the Centipede. (First AoSHIELD episode)
The AoSHIELD episodes are based after IM3.
EDIT: After reading points in the comment made by Oliver_C, I did some more checking on several other websites. There is a very specific timeline given up to the time of The Avengers given by Marvel Studios which comes from Art of the Avengers. This is the only "official" Marvel release I can find showing a timeline. On this webpage (albeit not official), there is a very specific timeline which shows a video chapter-by-chapter timeline showing the AoSHIELD happening after IM3. (I have updated the timeline above to reflect this.) This makes more sense than my original timeline and accounts for discrepancies as described by Oliver_C. The notes in the two wikis which provide the "6 month" and "1 year" references are an "about".
Further to Paulster's great answer - considering the next episode of Agents of SHIELD takes place immediately after the events of Thor: The Dark World, and will not only be referencing it but will also incorporate a possible piece of Asgardian (or other realm) technology, I believe the AoS storyline is running concurrent to the Marvel cinematic universe.
So our team shows up in the wake of what happened in Greenwich, and we’re cleaning up. We’re looking for other Asgardian or alien -- we don’t use the words “dark elves” or anything like that -- but we’re looking for other alien material, because as we’ve learned from other episodes, if a Chitauri or somebody leaves something laying around, it can lead to trouble.
Captain America: The First Avenger takes place in 1942-1945, ending in early 2012. Agent Carter Season 1 takes place in early 1946 with the One-Shot technically being the very last episode in the same year. Iron Man takes place in 2010. Iron Man 2, The Incredible Hulk & Thor take place in 2011. The Avengers takes place in June of 2012. Dare Devil takes place sometime after the events of The Avengers also in 2012. Iron Man 3 takes place in December of 2012. Agents of Shield season 1 takes place September 2013-May 2014. Thor: The Dark World takes place in November 2013. Captain America: The Winter Soldier takes place in April of 2014. Guardians of the Galaxy takes place in 2014 in the Andromeda Galaxy. Agents of Shield season 2 takes place 6 months after season 1 ends, November 2014- sometime in 2015.