This is only speculation but I imagine they put 11:55pm because putting 12:00am or later would have them end on the following day. Perhaps this logistical issue would mess around with their schedule template on the Sched.com website, which lists the bands by day.
I had the same suspicion. If this is the only bug they need to work out before posting the fraking schedule I'll be pissed. At this point I don't think they can come up with an excuse that would satisfy me though.
I just figured that was just there way of not letting anyone know the fact they were definitely going to break whatever curfew is in place, kinda like being in high school and telling your parents before you go out that night "OF COURSE I'll be back by midnight."