In May 2020, prior to the release of the Day6's album
The Book of Us: The Demon, it was announced that the group would cancel promotions of the album and go on hiatus due to the mental health issues of some members, later revealed to be leader Sungjin and guitarist
Jae. Even of Day was formed with the remaining active members: bassist
Young K, keyboardist
Wonpil, and drummer
Dowoon. On August 6, following rumors of the sub-unit, the group's label
JYP Entertainment confirmed the sub-unit's formation, with details of its debut to follow. On August 11, JYPE officially introduced
Day6's first sub-unit project, Even of Day, five years since their debut. JYPE released a teaser image announcing the unit on Day6's social media pages. The unit name "Even of Day" was given by
Park Jin-young, JYPE's founder: "Even" is an old way of saying "night", so "Even of Day" conveys the message that a bright day will finally come after a dark night. On August 13, they dropped the teaser schedule for their debut with the EP
The Book of Us: Gluon, which marked the fourth installment of Day6's
The Book of Us series
. The Book of Us: Gluon, alongside its lead single "Where the Sea Sleeps," was released on August 31. The album debuted at number three on the Gaon Album Chart. Even of Day partook in the first segment of the web music show
Secret Atelier where they released a single, "So, This Is Love," on January 15, 2021, as a result of the show. On January 24, Even of Day held their first online concert, Online Party Night: The Arcane Salon. On July 5, the group made their first comeback with their second EP
Right Through Me and its title track of the same name. Even of Day held their second concert, Day6 Even of Day: Right Through Me, through the online concert platform
Beyond Live on August 8. On August 31, 2022, the unit released a special music video for "Darling on the Beach". == Members ==