"One Day" is a song by the South Korean boy groups 2AM and 2PM, Oneday.

[2] The song is the main theme song for the documentary movie "Beyond the Oneday ~Story of 2PM & 2AM~", which was broadcast in Japan starting on June 30.

[3][4] The single was released in twelve editions: "One Day" is an original Japanese song, composed by Yu Shimoji, Faya, Super Changddai and Michael Yano.

The B-side "No Goodbyes" is an original Japanese song, written and composed by 2PM's MinJun and Emyli.

"Angel", CD Only bonus track, is originally a Korean song from 2PM's debut single Hottest Time of the Day.