St Valentine, if he was in fact a Saint and not a myth is not on the calendar. No Feast day official or otherwise. Halloween? Well we have a solemn Mass for the dead that day, costumes are not allowed. In my Diocese they do not allow the kids to dress up at the parish schools anyway.
I am all for having a party. Maybe we should make a bigger deal for Saint Joseph. March 19th! :)
My bad! All Souls should be All Saints.