I'm sorry, I was looking at february dates for some reason. My guess is that they haven't loaded schedules for March yet, as everything beyond march is not bookable.

IIRC they open up their bookings 62 days before the day of departure. If you want to look at schedules, look at http://www.bahn.de/

I was a bit incorrect about night trains too... bahn.de shows a possibility of buying a ticket where you'd leave Madrid around 8PM, have a 2:35 connection in Palencia, get on an overnight train around midnight, and arrive in Barcelona around 8AM. Too much hassle, IMO.