Wonderful Days (also known as Sky Blue) is a South Korean animated science fiction film, released in 2003, written and directed by Kim Moon-saeng.

A technologically advanced city named Ecoban was built and it harvests energy from the DELOS System, which uses pollution in a carbonite catalyzed reaction to generate power.

He ends up in a love triangle with his childhood friend, a girl named Jay, and her superior, Ecoban security commander Cade as his rival.

Other Western countries such as France and Finland have kept its original title—which is a Hangul transliteration of the English phrase "Wonderful Days" (it would be rendered in Revised Romanization as "Wondeopul Deijeu").

According to adaptation director Hiroshi Yamaga, Gainax changed the direction of the film to make the dialogue less "alien" to Japanese viewers.