In a long promo interview in September 2007, Dave Gahan was asked about every song off 'Hourglass' including this one:
"Twenty-one days was like, Andrew played these sort of discordant chords on a guitar and almost out of tune and it inspired this, I know it had a, to me it had a very Stooges feel about it. At the time visually there was this, outside of the window, my studio is in a very busy part of New York and um across the road we used to have a view of the river and there was a, there was a building being built and it seemed to go up so fast like a, it's kind of another one of those time things that er, that came up on the album. And very quickly the view that we had of the river was being taken away and it kind of really bothered me, you know that I had no control over changing that, and the speed that what was visually outside of my window changed, so it became like the sort of er, inspired the song and certainly the lyrics and I started thinking a lot about, I don't know thinking that you've got, you know just when you feel you've got, you're in a real comfortable place and everything is going, there's something comes and shakes it all up. So that song kind of came from there."
Dates where 21 Days was played
21 Days has never been played live.