How to determne phase shift of filtered analog signal

Hello

I used a low pass filter commonly as Butterworth of second order with fs=500 (so Fn=fs/2) and cut-off freq FC = 30 Hz, on a analog time domine data.

[b,a]=butter(2,Fc/Fn,'low');

The output of the filtered data was a smooth signal, but their is phase shift, can I quantify it. is their a command in matlab to determine.

--- Thanks