Overview of which DataSource contains calendar release data ?

[negue]

Is there any overview for this?

I have "One Piece" as Anime this one shows up nicely in the calendar, but the Manga does not - means either this Data Source itself has no data or just for "One Piece" Manga itself is has no data available

[FuzzyGrim]

No, Yamtrack doesn't display manga chapter releases on the calendar. Currently, it only shows the manga's end date with its last ever chapter, provided by MyAnimeList. I haven't found a good API provider for querying manga chapter release dates.

[negue]

I see ok, haven't checked MyAnimeList yet,

but MangaUpdates does have Releases: https://api.mangaupdates.com/#tag/releases/operation/listReleasesByDay - maybe that one could be used