Well that depends on weather you apply to the egoist approach to ethics or the utilitarian. In terms of the egoist approach he is doing what's best for him, therefore it's ethical... However, he is not doing what's best for everyone, as changing dates would be a hassle to the school as well as the other person, so that's unethical.... You know, you could also say that everyone not switching with him is acting unethically since it should be our duty to help someone in need per the Divine Command Theory of ethics.....
Regardless, I think he just wants in before December 1.