The Agile Manifesto never came out and said so, but it only ever made any sense if you give up the idea of a fixed delivery date. Of course, the idea of a fixed delivery date for a software project never made sense in the first place, but you’ll have to pry that nonsense from their cold dead hands. Big-A “Agile” is an attempt to keep what they (think they) want… so it ends up being useless.
Or you can have a fixed delivery date, but not a fixed feature set. If a feature isn't ready by the release date, it gets pushed to the next release. If you deliver often as agile encourages, this is a fairly short delay.
