This question already has an answer here:
- don't click the Answer Your Own Question checkbox
- then find the correct answer to your question
- and you answer your own question before 2 days go by
- you can't select your own answer
You've figured out the the correct answer to solve your own problem. Why should the delay exist?
I can understand a 10 minute delay to hinder new users, but a 2 day delay makes no sense.
There is nothing that prevents the author from selecting a different answer at a later time, should one prove to be better, but if there is a somewhat specific question and the author figures out the answer earlier than the 2 day time frame, there shouldn't be anything preventing him from selecting his answer.