# How to solve the advection equation in 2 dimension using the Crank-Nicolson method?

I've an equation like this to solve with the crank-nicolson method

$$U_t -\frac{y}{2} U_x + \frac{x}{2}U_y = 0,$$

where $x$ and $y$ are: [-2,5:2,5] and the time $T$ is from $0$ to $2\pi$. Is there anyone who can help me? I have to solve it in a matlab code. thanks everyone. I'm sorry for my english.