The Best Day is the first Japanese best album by DAY6. It was released on June 6, 2018.
The songs are from every digital singles released each month by the group in 2017 and the title tracks for their two first mini-album The Day and Daydream, in their original Korean version. Three new songs are also included: the English versions of "Congratulations" and "You Were Beautiful", and the Japanese version of "I Wait".
The physical release comes in two versions: a regular CD edition and a limited CD+DVD+Photobook edition. On digital platforms, the album was released as a four-track EP including the three new songs and "Dance Dance".