Overnight train reservation question

Hi everybody,
my problem is the following:
I woul like to go from sapporo to tokyo by hokutosei overnight train on the 12th of may 2008. i will arrive in japan on the 6th of may, and was planning to the train station then as soon as possible to make a reservation. i am going to have a rail pass for one week and was intending to use it on the reservation for the overnight ride ( i know i have to pay additional fare but that is fine). the problem is that i wanted to use the rail pass the week from 12th to 19th may to travel around japan, but i guess i already need it when i make the reservation for the overnight ride to tokyo? would that mean that i have to get a two week rail pass if i plan to make the reservation on the 7th of may?
thanks for your help!
tobi

I would like to go from sapporo to tokyo by hokutosei overnight train on the 12th of may 2008. i will arrive in japan on the 6th of may, and was planning to the train station then as soon as possible to make a reservation. i am going to have a rail pass for one week and was intending to use it on the reservation for the overnight ride ( i know i have to pay additional fare but that is fine). the problem is that i wanted to use the rail pass the week from 12th to 19th may to travel around japan, but i guess i already need it when i make the reservation for the overnight ride to tokyo? would that mean that i have to get a two week rail pass if i plan to make the reservation on the 7th of may?

You can have the starting date of your JR Pass postdated up to one month ahead.

If you land at Narita, you might do so at Narita Airport Station on 6th May. You can make a sleeper berth reservation at the same time. Reportedly the station clerks there understand English better than at other places.

Please be reminded that one of the two Hokutosei trains stopped running on 15th March, last Saturday. Only one daily Hokutosei which leaves Sapporo at 17:12 is available.

thank you very much! i did not know that it is possible to get another starting date from the one when you get the pass.
thanks again, take care!