Wake Me Up When September Ends song meaning

[Mixed Titles]

The song is dedicated towards Billie's (Billie Joe Armstrong lead singer of Greenday) father who died of throat cancer when Billie was a child.
In this song Armstrong reveals his feelings about his father who died in September of 1982 when Armstrong was 10 years old. However this is not the only meaning that this song bears. For most Americans the month of September is associated with the 9/11 terrorist attacks of 2001. A lot of people have lost their loved ones to that tragedy and September (which comes on the album as track 11) is connected not only to the death of the author's father, but also to the families of the victims of 9/11, and the pain of losing loved ones in general. This is a song of wisdom and acceptance. "Drenched in my pain again, becoming who we are" - the realization of the fact that everything we go through, all the pain and losses, all the hardships we meet along the way are meant to make us stronger and shape our personalities.
In the video for this song we see a young couple that gets separated by the circumstances. This shows the director's view of the song: we should treasure our loved ones and never take them for granted, because they can be taken away from us any moment.

Wake Me Up When September Ends is believed to be the most detached song of the album because it mostly portrays the author's personal feelings and is barely linked to the story of the album.