Green Day have begun work on their follow-up to 2009's 21st Century Breakdown, according to a tweet from frontman Billie Joe Armstrong. He writes: "Happy Valantine's day! Officially started recording the new record today. It's FUCK TIME!!!!"

The band has been writing new material since at least June, and several new songs have surfaced in Green Day's sets over the past year, including "Carpe Diem" and "Stray Heart." Whether or not either song makes the final album remains to be seen, of course.