I know that in an interview (translated at http://heartstation.org/?page_id=1008 ), Nomura, the creator of KH, mentioned that it took him a year to convince Disney to open up their copyright for the game. Beyond that, he did not mention how long it took to program/animate or any reference dates.
Exert from above link:
"Kandou: For about one year, Nomura did it all alone. And so, it was a one-man project. For that whole time, he continued to work on his plan as he negotiated with Disney."