Does anyone know what this series is?

Question

There is a book series that deals with the days of the week and a boy (the protagonist) having to battle them to save the world or something. (Each day of the week is the name of one of the bosses that the boy has to battle, each one more powerful than the other starting from Monday.) I think the third book in the series is labeled "Drowning Wednesday".

Answer 1

It is called "The keys to the kingdom" by Garth Nix.