It usually takes approximately 10 days for a contract to become official. In Masahiro Tanaka‘s case, it only took four hours.
The Yankees have announced that the Masahiro Tanaka deal is official and he has been placed on the 40 man roster. In a corresponding move, the Yankees designated David Huff for assignment.
So if you were skeptical about the Tanaka deal falling through–you can now put your fears to rest.