Does it mention that in the book?
Yupp, it does.
Inthe Garage, when Marcone shows up, he nsays something along the lines of
"I'm aware of your rather special resilience this time of the month"
When the Lycanthropes confront harry on the roadside, their leader says something about his Leg not healing completely the last night, hinting at the fact that they only have their power under a full moon, as the power didn't work during the day.
There may be more, but i'd have to check the book, and i don't want to right now