The toolbox date command is incredibly stupid.
It doesn't even handle the -u (UTC) flag correctly.
It also has no error handling, one typo gives you a date in 1970.
I wrote adbtime.exe a while ago (it's in the signature).
If you have the adb server running on your host already, just type:
I use this in combination with adbsync.exe to make sure my Nook is ready for the world before I go out the door.