Function pins 

pub(crate) fn pins(
    shared: &Shared,
    events: &[Occurrence],
    tasks: &[Task],
    now: &Zoned,
) -> Blocks

The tasks pinned to a time as of now: their blocks among events (the plan’s weeks, every calendar) and in the calendars made or chosen for blocks, further ahead; those whose deletion waits (“Undo”) aside. The blocks found are kept for what moves them.