Tuesday, 13 March -- Depart Denver
Wednesday, 14 March -- Arrive Narita, spend the night in Narita
Thursday, 15 March -- Arrive Tokyo, staying until...
Sunday, 18 March -- Shinkansen to Akita, staying until...
Thursday, 22 March -- Shinkansen back to Tokyo
Friday, 23 March -- Party in Tokyo! 誕生日おめでとう to me!
Thursday, 29 March -- Depart Narita, arriving in Denver 34 minutes later (ah, the wonder of timezones).
The most likely change is swapping the Akita leg to after instead of before my birthday; either way, I want to be in Tokyo on the day itself. Doing that before is still better due to time constraints, though.
I'll keep you apprised of the schedule -- other than the flight times and my birthday, I still have a great deal of flexibility. And ultimately my birthday doesn't have to be spent in Tokyo, that's just a strong preference -- I want to spend that day/night with friends there.