Six Phases of the Marvel Universe

World War II (Captain America 1)

From the end of World War II to Tony Stark announcing himself as Iron Man (including Captain Marvel, about 1945-2008)

Iron Man reveals his identity until the end of The Avengers 1 (about 2008-2012)

After The Avengers 1 to before The Avengers 2 (about 2012-2015)

After Avengers 2 until the end of the Civil War in Captain America 3 (around 2015-2016)

After the Civil War until before Avengers 4 (around 2016-2018)