"Werewolf, Vampire, and normal Sim skin types are now updating correctly at proper times."
The older info:
There seems to be a conflict with the werewolf code and custom skintones. If your sim is a werewolf but doesn't change into his werewolf skin in the evening, or doesn't change back to his regular skin in the morning, you are experiencing this bug.
Until we get a patch from Maxis and hopefully this is fixed, you can try this download by pioupiou