Airlines only care (if they care at all) about the flight. They do not give a stuff about what plans you may have made when you've got there, and the law is pretty much on their side to agree with them.
Do you have a source?
Presumably a contract exists for transport from A to B on a certain date (or, if reasonable, within a certain date).
If a situation really exists whereby you can purchase a ticket, they are unable to carry you, yet are entitled to simply offer you a new flight 3 months later, then something is wrong. I'm not entirely sure this is the case.