I'm gonna disagree with you there, you realize he's going on extended leave, not quitting the job. I work for a major corporation also, you should give them the notice as soon as you have the actual ship date. Actual ship date is reliable this time around as plenty are shipping out (unless you have a med issue)

No one with half a brain is going to believe that you received a ship date 2 days away, they can't fire you for military leave but trust me they can find other reasons / create animosity in the future.

I was lucky to have a ship date about 45 days away, they weren't thrilled but it gave them plenty of time to move things around while I'm gone.

At this point hope that it's August or later, although you may get something for April or May... I know that the minimum time they give is 3 weeks out, so it won't be sooner than that if that makes a difference.