Function agenda_read 

pub(crate) fn agenda_read(
    from: i64,
    to: i64,
    removed: &BTreeSet<PathBuf>,
    skipped: &BTreeSet<(PathBuf, i64)>,
) -> Vec<Occurrence>

The calendars’ events from from to to, those whose deletion waits aside, before their tasks are known (agenda_items; the home card marks them with the tasks of its plan).