User blog comment:B214/Shin DxD 1 discussion/@comment-78.4.96.213-20180721163242/@comment-3965848-20180723171607

@Demonic Ex is set between Vol. 19 and maybe 16, it even foreshadowed events that would happen later like creating more Durandals, Ajuka is the only Maou left, Azazel is no longer in charge of Grigori and the upcoming battle with ExE. So it is canon.

Ex just explains how BorN was changed due to a time anomaly cause by Loki from a possible future, so BorN is seen as a separate universe/timeline from the novels and the current anime seasons.