There is a land where every inhabitant is either a day-knight or a night-knight. Day-knights tell the truth in the day and lie at night. Night-knights lie in the day and tell the truth at night.

Members of the Smith family are day-knights and members of the Jones family are night-knights.

Three inhabitants Al, Ben and Cal approach a visitor to the island. It is known that precisely two of them are members of the Jones family and the remaining one is a member of the Smith family.

They say:

Al: Ben belongs to the Jones family. 
Ben: Cal belongs to the Jones family. 
Cal: Al’s surname is Smith.

What are the surnames of the three inhabitants? Is it day or night?