How many days notice before a bill due date? (apartment, lease)

[courie969]

In the apartment I am renting, it indicates that I am to pay a certain percentage of the gas/water bill every month, payable to the landlord. It does not, however, indicate -when- it's due, or -when- I will get the bill from the landlord for it.
However, I've been here since July and the paper she gives me every month tells me the amount due and "please pay by the 21st." So, that's what I've been doing. I have always gotten that paper telling me the amount by the 10th of every month, giving me 11 days to pay the bill to her.
It's the 13th and I still have not gotten that bill... I know that she has received the bill as I pay for separate utilities and it's from the same company, and because I've gotten my own bill I know that she has gotten the bill as well.
My question is this: Is there any sort of law (outside of maybe what my lease indicates, since it doesn't not indicate -anything- about this) .. that says my landlord has to give me the bill for something so many days before the date said bill is due?
Thanks!